<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux/kernel/bpf, branch v6.3</title>
<subtitle>Mirror of https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/
</subtitle>
<id>https://git.shady.money/linux/atom?h=v6.3</id>
<link rel='self' href='https://git.shady.money/linux/atom?h=v6.3'/>
<link rel='alternate' type='text/html' href='https://git.shady.money/linux/'/>
<updated>2023-04-19T17:18:18Z</updated>
<entry>
<title>bpf: Fix incorrect verifier pruning due to missing register precision taints</title>
<updated>2023-04-19T17:18:18Z</updated>
<author>
<name>Daniel Borkmann</name>
<email>daniel@iogearbox.net</email>
</author>
<published>2023-04-11T15:24:13Z</published>
<link rel='alternate' type='text/html' href='https://git.shady.money/linux/commit/?id=71b547f561247897a0a14f3082730156c0533fed'/>
<id>urn:sha1:71b547f561247897a0a14f3082730156c0533fed</id>
<content type='text'>
Juan Jose et al reported an issue found via fuzzing where the verifier's
pruning logic prematurely marks a program path as safe.

Consider the following program:

   0: (b7) r6 = 1024
   1: (b7) r7 = 0
   2: (b7) r8 = 0
   3: (b7) r9 = -2147483648
   4: (97) r6 %= 1025
   5: (05) goto pc+0
   6: (bd) if r6 &lt;= r9 goto pc+2
   7: (97) r6 %= 1
   8: (b7) r9 = 0
   9: (bd) if r6 &lt;= r9 goto pc+1
  10: (b7) r6 = 0
  11: (b7) r0 = 0
  12: (63) *(u32 *)(r10 -4) = r0
  13: (18) r4 = 0xffff888103693400 // map_ptr(ks=4,vs=48)
  15: (bf) r1 = r4
  16: (bf) r2 = r10
  17: (07) r2 += -4
  18: (85) call bpf_map_lookup_elem#1
  19: (55) if r0 != 0x0 goto pc+1
  20: (95) exit
  21: (77) r6 &gt;&gt;= 10
  22: (27) r6 *= 8192
  23: (bf) r1 = r0
  24: (0f) r0 += r6
  25: (79) r3 = *(u64 *)(r0 +0)
  26: (7b) *(u64 *)(r1 +0) = r3
  27: (95) exit

The verifier treats this as safe, leading to oob read/write access due
to an incorrect verifier conclusion:

  func#0 @0
  0: R1=ctx(off=0,imm=0) R10=fp0
  0: (b7) r6 = 1024                     ; R6_w=1024
  1: (b7) r7 = 0                        ; R7_w=0
  2: (b7) r8 = 0                        ; R8_w=0
  3: (b7) r9 = -2147483648              ; R9_w=-2147483648
  4: (97) r6 %= 1025                    ; R6_w=scalar()
  5: (05) goto pc+0
  6: (bd) if r6 &lt;= r9 goto pc+2         ; R6_w=scalar(umin=18446744071562067969,var_off=(0xffffffff00000000; 0xffffffff)) R9_w=-2147483648
  7: (97) r6 %= 1                       ; R6_w=scalar()
  8: (b7) r9 = 0                        ; R9=0
  9: (bd) if r6 &lt;= r9 goto pc+1         ; R6=scalar(umin=1) R9=0
  10: (b7) r6 = 0                       ; R6_w=0
  11: (b7) r0 = 0                       ; R0_w=0
  12: (63) *(u32 *)(r10 -4) = r0
  last_idx 12 first_idx 9
  regs=1 stack=0 before 11: (b7) r0 = 0
  13: R0_w=0 R10=fp0 fp-8=0000????
  13: (18) r4 = 0xffff8ad3886c2a00      ; R4_w=map_ptr(off=0,ks=4,vs=48,imm=0)
  15: (bf) r1 = r4                      ; R1_w=map_ptr(off=0,ks=4,vs=48,imm=0) R4_w=map_ptr(off=0,ks=4,vs=48,imm=0)
  16: (bf) r2 = r10                     ; R2_w=fp0 R10=fp0
  17: (07) r2 += -4                     ; R2_w=fp-4
  18: (85) call bpf_map_lookup_elem#1   ; R0=map_value_or_null(id=1,off=0,ks=4,vs=48,imm=0)
  19: (55) if r0 != 0x0 goto pc+1       ; R0=0
  20: (95) exit

  from 19 to 21: R0=map_value(off=0,ks=4,vs=48,imm=0) R6=0 R7=0 R8=0 R9=0 R10=fp0 fp-8=mmmm????
  21: (77) r6 &gt;&gt;= 10                    ; R6_w=0
  22: (27) r6 *= 8192                   ; R6_w=0
  23: (bf) r1 = r0                      ; R0=map_value(off=0,ks=4,vs=48,imm=0) R1_w=map_value(off=0,ks=4,vs=48,imm=0)
  24: (0f) r0 += r6
  last_idx 24 first_idx 19
  regs=40 stack=0 before 23: (bf) r1 = r0
  regs=40 stack=0 before 22: (27) r6 *= 8192
  regs=40 stack=0 before 21: (77) r6 &gt;&gt;= 10
  regs=40 stack=0 before 19: (55) if r0 != 0x0 goto pc+1
  parent didn't have regs=40 stack=0 marks: R0_rw=map_value_or_null(id=1,off=0,ks=4,vs=48,imm=0) R6_rw=P0 R7=0 R8=0 R9=0 R10=fp0 fp-8=mmmm????
  last_idx 18 first_idx 9
  regs=40 stack=0 before 18: (85) call bpf_map_lookup_elem#1
  regs=40 stack=0 before 17: (07) r2 += -4
  regs=40 stack=0 before 16: (bf) r2 = r10
  regs=40 stack=0 before 15: (bf) r1 = r4
  regs=40 stack=0 before 13: (18) r4 = 0xffff8ad3886c2a00
  regs=40 stack=0 before 12: (63) *(u32 *)(r10 -4) = r0
  regs=40 stack=0 before 11: (b7) r0 = 0
  regs=40 stack=0 before 10: (b7) r6 = 0
  25: (79) r3 = *(u64 *)(r0 +0)         ; R0_w=map_value(off=0,ks=4,vs=48,imm=0) R3_w=scalar()
  26: (7b) *(u64 *)(r1 +0) = r3         ; R1_w=map_value(off=0,ks=4,vs=48,imm=0) R3_w=scalar()
  27: (95) exit

  from 9 to 11: R1=ctx(off=0,imm=0) R6=0 R7=0 R8=0 R9=0 R10=fp0
  11: (b7) r0 = 0                       ; R0_w=0
  12: (63) *(u32 *)(r10 -4) = r0
  last_idx 12 first_idx 11
  regs=1 stack=0 before 11: (b7) r0 = 0
  13: R0_w=0 R10=fp0 fp-8=0000????
  13: (18) r4 = 0xffff8ad3886c2a00      ; R4_w=map_ptr(off=0,ks=4,vs=48,imm=0)
  15: (bf) r1 = r4                      ; R1_w=map_ptr(off=0,ks=4,vs=48,imm=0) R4_w=map_ptr(off=0,ks=4,vs=48,imm=0)
  16: (bf) r2 = r10                     ; R2_w=fp0 R10=fp0
  17: (07) r2 += -4                     ; R2_w=fp-4
  18: (85) call bpf_map_lookup_elem#1
  frame 0: propagating r6
  last_idx 19 first_idx 11
  regs=40 stack=0 before 18: (85) call bpf_map_lookup_elem#1
  regs=40 stack=0 before 17: (07) r2 += -4
  regs=40 stack=0 before 16: (bf) r2 = r10
  regs=40 stack=0 before 15: (bf) r1 = r4
  regs=40 stack=0 before 13: (18) r4 = 0xffff8ad3886c2a00
  regs=40 stack=0 before 12: (63) *(u32 *)(r10 -4) = r0
  regs=40 stack=0 before 11: (b7) r0 = 0
  parent didn't have regs=40 stack=0 marks: R1=ctx(off=0,imm=0) R6_r=P0 R7=0 R8=0 R9=0 R10=fp0
  last_idx 9 first_idx 9
  regs=40 stack=0 before 9: (bd) if r6 &lt;= r9 goto pc+1
  parent didn't have regs=40 stack=0 marks: R1=ctx(off=0,imm=0) R6_rw=Pscalar() R7_w=0 R8_w=0 R9_rw=0 R10=fp0
  last_idx 8 first_idx 0
  regs=40 stack=0 before 8: (b7) r9 = 0
  regs=40 stack=0 before 7: (97) r6 %= 1
  regs=40 stack=0 before 6: (bd) if r6 &lt;= r9 goto pc+2
  regs=40 stack=0 before 5: (05) goto pc+0
  regs=40 stack=0 before 4: (97) r6 %= 1025
  regs=40 stack=0 before 3: (b7) r9 = -2147483648
  regs=40 stack=0 before 2: (b7) r8 = 0
  regs=40 stack=0 before 1: (b7) r7 = 0
  regs=40 stack=0 before 0: (b7) r6 = 1024
  19: safe
  frame 0: propagating r6
  last_idx 9 first_idx 0
  regs=40 stack=0 before 6: (bd) if r6 &lt;= r9 goto pc+2
  regs=40 stack=0 before 5: (05) goto pc+0
  regs=40 stack=0 before 4: (97) r6 %= 1025
  regs=40 stack=0 before 3: (b7) r9 = -2147483648
  regs=40 stack=0 before 2: (b7) r8 = 0
  regs=40 stack=0 before 1: (b7) r7 = 0
  regs=40 stack=0 before 0: (b7) r6 = 1024

  from 6 to 9: safe
  verification time 110 usec
  stack depth 4
  processed 36 insns (limit 1000000) max_states_per_insn 0 total_states 3 peak_states 3 mark_read 2

The verifier considers this program as safe by mistakenly pruning unsafe
code paths. In the above func#0, code lines 0-10 are of interest. In line
0-3 registers r6 to r9 are initialized with known scalar values. In line 4
the register r6 is reset to an unknown scalar given the verifier does not
track modulo operations. Due to this, the verifier can also not determine
precisely which branches in line 6 and 9 are taken, therefore it needs to
explore them both.

As can be seen, the verifier starts with exploring the false/fall-through
paths first. The 'from 19 to 21' path has both r6=0 and r9=0 and the pointer
arithmetic on r0 += r6 is therefore considered safe. Given the arithmetic,
r6 is correctly marked for precision tracking where backtracking kicks in
where it walks back the current path all the way where r6 was set to 0 in
the fall-through branch.

Next, the pruning logics pops the path 'from 9 to 11' from the stack. Also
here, the state of the registers is the same, that is, r6=0 and r9=0, so
that at line 19 the path can be pruned as it is considered safe. It is
interesting to note that the conditional in line 9 turned r6 into a more
precise state, that is, in the fall-through path at the beginning of line
10, it is R6=scalar(umin=1), and in the branch-taken path (which is analyzed
here) at the beginning of line 11, r6 turned into a known const r6=0 as
r9=0 prior to that and therefore (unsigned) r6 &lt;= 0 concludes that r6 must
be 0 (**):

  [...]                                 ; R6_w=scalar()
  9: (bd) if r6 &lt;= r9 goto pc+1         ; R6=scalar(umin=1) R9=0
  [...]

  from 9 to 11: R1=ctx(off=0,imm=0) R6=0 R7=0 R8=0 R9=0 R10=fp0
  [...]

The next path is 'from 6 to 9'. The verifier considers the old and current
state equivalent, and therefore prunes the search incorrectly. Looking into
the two states which are being compared by the pruning logic at line 9, the
old state consists of R6_rwD=Pscalar() R9_rwD=0 R10=fp0 and the new state
consists of R1=ctx(off=0,imm=0) R6_w=scalar(umax=18446744071562067968)
R7_w=0 R8_w=0 R9_w=-2147483648 R10=fp0. While r6 had the reg-&gt;precise flag
correctly set in the old state, r9 did not. Both r6'es are considered as
equivalent given the old one is a superset of the current, more precise one,
however, r9's actual values (0 vs 0x80000000) mismatch. Given the old r9
did not have reg-&gt;precise flag set, the verifier does not consider the
register as contributing to the precision state of r6, and therefore it
considered both r9 states as equivalent. However, for this specific pruned
path (which is also the actual path taken at runtime), register r6 will be
0x400 and r9 0x80000000 when reaching line 21, thus oob-accessing the map.

The purpose of precision tracking is to initially mark registers (including
spilled ones) as imprecise to help verifier's pruning logic finding equivalent
states it can then prune if they don't contribute to the program's safety
aspects. For example, if registers are used for pointer arithmetic or to pass
constant length to a helper, then the verifier sets reg-&gt;precise flag and
backtracks the BPF program instruction sequence and chain of verifier states
to ensure that the given register or stack slot including their dependencies
are marked as precisely tracked scalar. This also includes any other registers
and slots that contribute to a tracked state of given registers/stack slot.
This backtracking relies on recorded jmp_history and is able to traverse
entire chain of parent states. This process ends only when all the necessary
registers/slots and their transitive dependencies are marked as precise.

The backtrack_insn() is called from the current instruction up to the first
instruction, and its purpose is to compute a bitmask of registers and stack
slots that need precision tracking in the parent's verifier state. For example,
if a current instruction is r6 = r7, then r6 needs precision after this
instruction and r7 needs precision before this instruction, that is, in the
parent state. Hence for the latter r7 is marked and r6 unmarked.

For the class of jmp/jmp32 instructions, backtrack_insn() today only looks
at call and exit instructions and for all other conditionals the masks
remain as-is. However, in the given situation register r6 has a dependency
on r9 (as described above in **), so also that one needs to be marked for
precision tracking. In other words, if an imprecise register influences a
precise one, then the imprecise register should also be marked precise.
Meaning, in the parent state both dest and src register need to be tracked
for precision and therefore the marking must be more conservative by setting
reg-&gt;precise flag for both. The precision propagation needs to cover both
for the conditional: if the src reg was marked but not the dst reg and vice
versa.

After the fix the program is correctly rejected:

  func#0 @0
  0: R1=ctx(off=0,imm=0) R10=fp0
  0: (b7) r6 = 1024                     ; R6_w=1024
  1: (b7) r7 = 0                        ; R7_w=0
  2: (b7) r8 = 0                        ; R8_w=0
  3: (b7) r9 = -2147483648              ; R9_w=-2147483648
  4: (97) r6 %= 1025                    ; R6_w=scalar()
  5: (05) goto pc+0
  6: (bd) if r6 &lt;= r9 goto pc+2         ; R6_w=scalar(umin=18446744071562067969,var_off=(0xffffffff80000000; 0x7fffffff),u32_min=-2147483648) R9_w=-2147483648
  7: (97) r6 %= 1                       ; R6_w=scalar()
  8: (b7) r9 = 0                        ; R9=0
  9: (bd) if r6 &lt;= r9 goto pc+1         ; R6=scalar(umin=1) R9=0
  10: (b7) r6 = 0                       ; R6_w=0
  11: (b7) r0 = 0                       ; R0_w=0
  12: (63) *(u32 *)(r10 -4) = r0
  last_idx 12 first_idx 9
  regs=1 stack=0 before 11: (b7) r0 = 0
  13: R0_w=0 R10=fp0 fp-8=0000????
  13: (18) r4 = 0xffff9290dc5bfe00      ; R4_w=map_ptr(off=0,ks=4,vs=48,imm=0)
  15: (bf) r1 = r4                      ; R1_w=map_ptr(off=0,ks=4,vs=48,imm=0) R4_w=map_ptr(off=0,ks=4,vs=48,imm=0)
  16: (bf) r2 = r10                     ; R2_w=fp0 R10=fp0
  17: (07) r2 += -4                     ; R2_w=fp-4
  18: (85) call bpf_map_lookup_elem#1   ; R0=map_value_or_null(id=1,off=0,ks=4,vs=48,imm=0)
  19: (55) if r0 != 0x0 goto pc+1       ; R0=0
  20: (95) exit

  from 19 to 21: R0=map_value(off=0,ks=4,vs=48,imm=0) R6=0 R7=0 R8=0 R9=0 R10=fp0 fp-8=mmmm????
  21: (77) r6 &gt;&gt;= 10                    ; R6_w=0
  22: (27) r6 *= 8192                   ; R6_w=0
  23: (bf) r1 = r0                      ; R0=map_value(off=0,ks=4,vs=48,imm=0) R1_w=map_value(off=0,ks=4,vs=48,imm=0)
  24: (0f) r0 += r6
  last_idx 24 first_idx 19
  regs=40 stack=0 before 23: (bf) r1 = r0
  regs=40 stack=0 before 22: (27) r6 *= 8192
  regs=40 stack=0 before 21: (77) r6 &gt;&gt;= 10
  regs=40 stack=0 before 19: (55) if r0 != 0x0 goto pc+1
  parent didn't have regs=40 stack=0 marks: R0_rw=map_value_or_null(id=1,off=0,ks=4,vs=48,imm=0) R6_rw=P0 R7=0 R8=0 R9=0 R10=fp0 fp-8=mmmm????
  last_idx 18 first_idx 9
  regs=40 stack=0 before 18: (85) call bpf_map_lookup_elem#1
  regs=40 stack=0 before 17: (07) r2 += -4
  regs=40 stack=0 before 16: (bf) r2 = r10
  regs=40 stack=0 before 15: (bf) r1 = r4
  regs=40 stack=0 before 13: (18) r4 = 0xffff9290dc5bfe00
  regs=40 stack=0 before 12: (63) *(u32 *)(r10 -4) = r0
  regs=40 stack=0 before 11: (b7) r0 = 0
  regs=40 stack=0 before 10: (b7) r6 = 0
  25: (79) r3 = *(u64 *)(r0 +0)         ; R0_w=map_value(off=0,ks=4,vs=48,imm=0) R3_w=scalar()
  26: (7b) *(u64 *)(r1 +0) = r3         ; R1_w=map_value(off=0,ks=4,vs=48,imm=0) R3_w=scalar()
  27: (95) exit

  from 9 to 11: R1=ctx(off=0,imm=0) R6=0 R7=0 R8=0 R9=0 R10=fp0
  11: (b7) r0 = 0                       ; R0_w=0
  12: (63) *(u32 *)(r10 -4) = r0
  last_idx 12 first_idx 11
  regs=1 stack=0 before 11: (b7) r0 = 0
  13: R0_w=0 R10=fp0 fp-8=0000????
  13: (18) r4 = 0xffff9290dc5bfe00      ; R4_w=map_ptr(off=0,ks=4,vs=48,imm=0)
  15: (bf) r1 = r4                      ; R1_w=map_ptr(off=0,ks=4,vs=48,imm=0) R4_w=map_ptr(off=0,ks=4,vs=48,imm=0)
  16: (bf) r2 = r10                     ; R2_w=fp0 R10=fp0
  17: (07) r2 += -4                     ; R2_w=fp-4
  18: (85) call bpf_map_lookup_elem#1
  frame 0: propagating r6
  last_idx 19 first_idx 11
  regs=40 stack=0 before 18: (85) call bpf_map_lookup_elem#1
  regs=40 stack=0 before 17: (07) r2 += -4
  regs=40 stack=0 before 16: (bf) r2 = r10
  regs=40 stack=0 before 15: (bf) r1 = r4
  regs=40 stack=0 before 13: (18) r4 = 0xffff9290dc5bfe00
  regs=40 stack=0 before 12: (63) *(u32 *)(r10 -4) = r0
  regs=40 stack=0 before 11: (b7) r0 = 0
  parent didn't have regs=40 stack=0 marks: R1=ctx(off=0,imm=0) R6_r=P0 R7=0 R8=0 R9=0 R10=fp0
  last_idx 9 first_idx 9
  regs=40 stack=0 before 9: (bd) if r6 &lt;= r9 goto pc+1
  parent didn't have regs=240 stack=0 marks: R1=ctx(off=0,imm=0) R6_rw=Pscalar() R7_w=0 R8_w=0 R9_rw=P0 R10=fp0
  last_idx 8 first_idx 0
  regs=240 stack=0 before 8: (b7) r9 = 0
  regs=40 stack=0 before 7: (97) r6 %= 1
  regs=40 stack=0 before 6: (bd) if r6 &lt;= r9 goto pc+2
  regs=240 stack=0 before 5: (05) goto pc+0
  regs=240 stack=0 before 4: (97) r6 %= 1025
  regs=240 stack=0 before 3: (b7) r9 = -2147483648
  regs=40 stack=0 before 2: (b7) r8 = 0
  regs=40 stack=0 before 1: (b7) r7 = 0
  regs=40 stack=0 before 0: (b7) r6 = 1024
  19: safe

  from 6 to 9: R1=ctx(off=0,imm=0) R6_w=scalar(umax=18446744071562067968) R7_w=0 R8_w=0 R9_w=-2147483648 R10=fp0
  9: (bd) if r6 &lt;= r9 goto pc+1
  last_idx 9 first_idx 0
  regs=40 stack=0 before 6: (bd) if r6 &lt;= r9 goto pc+2
  regs=240 stack=0 before 5: (05) goto pc+0
  regs=240 stack=0 before 4: (97) r6 %= 1025
  regs=240 stack=0 before 3: (b7) r9 = -2147483648
  regs=40 stack=0 before 2: (b7) r8 = 0
  regs=40 stack=0 before 1: (b7) r7 = 0
  regs=40 stack=0 before 0: (b7) r6 = 1024
  last_idx 9 first_idx 0
  regs=200 stack=0 before 6: (bd) if r6 &lt;= r9 goto pc+2
  regs=240 stack=0 before 5: (05) goto pc+0
  regs=240 stack=0 before 4: (97) r6 %= 1025
  regs=240 stack=0 before 3: (b7) r9 = -2147483648
  regs=40 stack=0 before 2: (b7) r8 = 0
  regs=40 stack=0 before 1: (b7) r7 = 0
  regs=40 stack=0 before 0: (b7) r6 = 1024
  11: R6=scalar(umax=18446744071562067968) R9=-2147483648
  11: (b7) r0 = 0                       ; R0_w=0
  12: (63) *(u32 *)(r10 -4) = r0
  last_idx 12 first_idx 11
  regs=1 stack=0 before 11: (b7) r0 = 0
  13: R0_w=0 R10=fp0 fp-8=0000????
  13: (18) r4 = 0xffff9290dc5bfe00      ; R4_w=map_ptr(off=0,ks=4,vs=48,imm=0)
  15: (bf) r1 = r4                      ; R1_w=map_ptr(off=0,ks=4,vs=48,imm=0) R4_w=map_ptr(off=0,ks=4,vs=48,imm=0)
  16: (bf) r2 = r10                     ; R2_w=fp0 R10=fp0
  17: (07) r2 += -4                     ; R2_w=fp-4
  18: (85) call bpf_map_lookup_elem#1   ; R0_w=map_value_or_null(id=3,off=0,ks=4,vs=48,imm=0)
  19: (55) if r0 != 0x0 goto pc+1       ; R0_w=0
  20: (95) exit

  from 19 to 21: R0=map_value(off=0,ks=4,vs=48,imm=0) R6=scalar(umax=18446744071562067968) R7=0 R8=0 R9=-2147483648 R10=fp0 fp-8=mmmm????
  21: (77) r6 &gt;&gt;= 10                    ; R6_w=scalar(umax=18014398507384832,var_off=(0x0; 0x3fffffffffffff))
  22: (27) r6 *= 8192                   ; R6_w=scalar(smax=9223372036854767616,umax=18446744073709543424,var_off=(0x0; 0xffffffffffffe000),s32_max=2147475456,u32_max=-8192)
  23: (bf) r1 = r0                      ; R0=map_value(off=0,ks=4,vs=48,imm=0) R1_w=map_value(off=0,ks=4,vs=48,imm=0)
  24: (0f) r0 += r6
  last_idx 24 first_idx 21
  regs=40 stack=0 before 23: (bf) r1 = r0
  regs=40 stack=0 before 22: (27) r6 *= 8192
  regs=40 stack=0 before 21: (77) r6 &gt;&gt;= 10
  parent didn't have regs=40 stack=0 marks: R0_rw=map_value(off=0,ks=4,vs=48,imm=0) R6_r=Pscalar(umax=18446744071562067968) R7=0 R8=0 R9=-2147483648 R10=fp0 fp-8=mmmm????
  last_idx 19 first_idx 11
  regs=40 stack=0 before 19: (55) if r0 != 0x0 goto pc+1
  regs=40 stack=0 before 18: (85) call bpf_map_lookup_elem#1
  regs=40 stack=0 before 17: (07) r2 += -4
  regs=40 stack=0 before 16: (bf) r2 = r10
  regs=40 stack=0 before 15: (bf) r1 = r4
  regs=40 stack=0 before 13: (18) r4 = 0xffff9290dc5bfe00
  regs=40 stack=0 before 12: (63) *(u32 *)(r10 -4) = r0
  regs=40 stack=0 before 11: (b7) r0 = 0
  parent didn't have regs=40 stack=0 marks: R1=ctx(off=0,imm=0) R6_rw=Pscalar(umax=18446744071562067968) R7_w=0 R8_w=0 R9_w=-2147483648 R10=fp0
  last_idx 9 first_idx 0
  regs=40 stack=0 before 9: (bd) if r6 &lt;= r9 goto pc+1
  regs=240 stack=0 before 6: (bd) if r6 &lt;= r9 goto pc+2
  regs=240 stack=0 before 5: (05) goto pc+0
  regs=240 stack=0 before 4: (97) r6 %= 1025
  regs=240 stack=0 before 3: (b7) r9 = -2147483648
  regs=40 stack=0 before 2: (b7) r8 = 0
  regs=40 stack=0 before 1: (b7) r7 = 0
  regs=40 stack=0 before 0: (b7) r6 = 1024
  math between map_value pointer and register with unbounded min value is not allowed
  verification time 886 usec
  stack depth 4
  processed 49 insns (limit 1000000) max_states_per_insn 1 total_states 5 peak_states 5 mark_read 2

Fixes: b5dc0163d8fd ("bpf: precise scalar_value tracking")
Reported-by: Juan Jose Lopez Jaimez &lt;jjlopezjaimez@google.com&gt;
Reported-by: Meador Inge &lt;meadori@google.com&gt;
Reported-by: Simon Scannell &lt;simonscannell@google.com&gt;
Reported-by: Nenad Stojanovski &lt;thenenadx@google.com&gt;
Signed-off-by: Daniel Borkmann &lt;daniel@iogearbox.net&gt;
Co-developed-by: Andrii Nakryiko &lt;andrii@kernel.org&gt;
Signed-off-by: Andrii Nakryiko &lt;andrii@kernel.org&gt;
Reviewed-by: John Fastabend &lt;john.fastabend@gmail.com&gt;
Reviewed-by: Juan Jose Lopez Jaimez &lt;jjlopezjaimez@google.com&gt;
Reviewed-by: Meador Inge &lt;meadori@google.com&gt;
Reviewed-by: Simon Scannell &lt;simonscannell@google.com&gt;
</content>
</entry>
<entry>
<title>bpf: Adjust insufficient default bpf_jit_limit</title>
<updated>2023-03-21T19:43:05Z</updated>
<author>
<name>Daniel Borkmann</name>
<email>daniel@iogearbox.net</email>
</author>
<published>2023-03-20T14:37:25Z</published>
<link rel='alternate' type='text/html' href='https://git.shady.money/linux/commit/?id=10ec8ca8ec1a2f04c4ed90897225231c58c124a7'/>
<id>urn:sha1:10ec8ca8ec1a2f04c4ed90897225231c58c124a7</id>
<content type='text'>
We've seen recent AWS EKS (Kubernetes) user reports like the following:

  After upgrading EKS nodes from v20230203 to v20230217 on our 1.24 EKS
  clusters after a few days a number of the nodes have containers stuck
  in ContainerCreating state or liveness/readiness probes reporting the
  following error:

    Readiness probe errored: rpc error: code = Unknown desc = failed to
    exec in container: failed to start exec "4a11039f730203ffc003b7[...]":
    OCI runtime exec failed: exec failed: unable to start container process:
    unable to init seccomp: error loading seccomp filter into kernel:
    error loading seccomp filter: errno 524: unknown

  However, we had not been seeing this issue on previous AMIs and it only
  started to occur on v20230217 (following the upgrade from kernel 5.4 to
  5.10) with no other changes to the underlying cluster or workloads.

  We tried the suggestions from that issue (sysctl net.core.bpf_jit_limit=452534528)
  which helped to immediately allow containers to be created and probes to
  execute but after approximately a day the issue returned and the value
  returned by cat /proc/vmallocinfo | grep bpf_jit | awk '{s+=$2} END {print s}'
  was steadily increasing.

I tested bpf tree to observe bpf_jit_charge_modmem, bpf_jit_uncharge_modmem
their sizes passed in as well as bpf_jit_current under tcpdump BPF filter,
seccomp BPF and native (e)BPF programs, and the behavior all looks sane
and expected, that is nothing "leaking" from an upstream perspective.

The bpf_jit_limit knob was originally added in order to avoid a situation
where unprivileged applications loading BPF programs (e.g. seccomp BPF
policies) consuming all the module memory space via BPF JIT such that loading
of kernel modules would be prevented. The default limit was defined back in
2018 and while good enough back then, we are generally seeing far more BPF
consumers today.

Adjust the limit for the BPF JIT pool from originally 1/4 to now 1/2 of the
module memory space to better reflect today's needs and avoid more users
running into potentially hard to debug issues.

Fixes: fdadd04931c2 ("bpf: fix bpf_jit_limit knob for PAGE_SIZE &gt;= 64K")
Reported-by: Stephen Haynes &lt;sh@synk.net&gt;
Reported-by: Lefteris Alexakis &lt;lefteris.alexakis@kpn.com&gt;
Signed-off-by: Daniel Borkmann &lt;daniel@iogearbox.net&gt;
Link: https://github.com/awslabs/amazon-eks-ami/issues/1179
Link: https://github.com/awslabs/amazon-eks-ami/issues/1219
Reviewed-by: Kuniyuki Iwashima &lt;kuniyu@amazon.com&gt;
Link: https://lore.kernel.org/r/20230320143725.8394-1-daniel@iogearbox.net
Signed-off-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
</content>
</entry>
<entry>
<title>Merge branch 'bpf: Allow reads from uninit stack'</title>
<updated>2023-03-13T20:21:22Z</updated>
<author>
<name>Alexei Starovoitov</name>
<email>ast@kernel.org</email>
</author>
<published>2023-03-13T20:20:58Z</published>
<link rel='alternate' type='text/html' href='https://git.shady.money/linux/commit/?id=a33a6eaa19d3af261e8708bfc8ba62020703117f'/>
<id>urn:sha1:a33a6eaa19d3af261e8708bfc8ba62020703117f</id>
<content type='text'>
Merge commit bf9bec4cb3a4 ("Merge branch 'bpf: Allow reads from uninit stack'")
from bpf-next to bpf tree to address verification issues in some programs
due to stack usage.

Signed-off-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
</content>
</entry>
<entry>
<title>Merge tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf</title>
<updated>2023-03-07T04:28:00Z</updated>
<author>
<name>Jakub Kicinski</name>
<email>kuba@kernel.org</email>
</author>
<published>2023-03-07T04:28:00Z</published>
<link rel='alternate' type='text/html' href='https://git.shady.money/linux/commit/?id=757b56a6c7bbaed0d005b60b3996ee5a04cf2d8d'/>
<id>urn:sha1:757b56a6c7bbaed0d005b60b3996ee5a04cf2d8d</id>
<content type='text'>
Daniel Borkmann says:

====================
pull-request: bpf 2023-03-06

We've added 8 non-merge commits during the last 7 day(s) which contain
a total of 9 files changed, 64 insertions(+), 18 deletions(-).

The main changes are:

1) Fix BTF resolver for DATASEC sections when a VAR points at a modifier,
   that is, keep resolving such instances instead of bailing out,
   from Lorenz Bauer.

2) Fix BPF test framework with regards to xdp_frame info misplacement
   in the "live packet" code, from Alexander Lobakin.

3) Fix an infinite loop in BPF sockmap code for TCP/UDP/AF_UNIX,
   from Liu Jian.

4) Fix a build error for riscv BPF JIT under PERF_EVENTS=n,
   from Randy Dunlap.

5) Several BPF doc fixes with either broken links or external instead
   of internal doc links, from Bagas Sanjaya.

* tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf:
  selftests/bpf: check that modifier resolves after pointer
  btf: fix resolving BTF_KIND_VAR after ARRAY, STRUCT, UNION, PTR
  bpf, test_run: fix &amp;xdp_frame misplacement for LIVE_FRAMES
  bpf, doc: Link to submitting-patches.rst for general patch submission info
  bpf, doc: Do not link to docs.kernel.org for kselftest link
  bpf, sockmap: Fix an infinite loop error when len is 0 in tcp_bpf_recvmsg_parser()
  riscv, bpf: Fix patch_text implicit declaration
  bpf, docs: Fix link to BTF doc
====================

Link: https://lore.kernel.org/r/20230306215944.11981-1-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski &lt;kuba@kernel.org&gt;
</content>
</entry>
<entry>
<title>btf: fix resolving BTF_KIND_VAR after ARRAY, STRUCT, UNION, PTR</title>
<updated>2023-03-06T19:44:13Z</updated>
<author>
<name>Lorenz Bauer</name>
<email>lorenz.bauer@isovalent.com</email>
</author>
<published>2023-03-06T11:21:37Z</published>
<link rel='alternate' type='text/html' href='https://git.shady.money/linux/commit/?id=9b459804ff9973e173fabafba2a1319f771e85fa'/>
<id>urn:sha1:9b459804ff9973e173fabafba2a1319f771e85fa</id>
<content type='text'>
btf_datasec_resolve contains a bug that causes the following BTF
to fail loading:

    [1] DATASEC a size=2 vlen=2
        type_id=4 offset=0 size=1
        type_id=7 offset=1 size=1
    [2] INT (anon) size=1 bits_offset=0 nr_bits=8 encoding=(none)
    [3] PTR (anon) type_id=2
    [4] VAR a type_id=3 linkage=0
    [5] INT (anon) size=1 bits_offset=0 nr_bits=8 encoding=(none)
    [6] TYPEDEF td type_id=5
    [7] VAR b type_id=6 linkage=0

This error message is printed during btf_check_all_types:

    [1] DATASEC a size=2 vlen=2
        type_id=7 offset=1 size=1 Invalid type

By tracing btf_*_resolve we can pinpoint the problem:

    btf_datasec_resolve(depth: 1, type_id: 1, mode: RESOLVE_TBD) = 0
        btf_var_resolve(depth: 2, type_id: 4, mode: RESOLVE_TBD) = 0
            btf_ptr_resolve(depth: 3, type_id: 3, mode: RESOLVE_PTR) = 0
        btf_var_resolve(depth: 2, type_id: 4, mode: RESOLVE_PTR) = 0
    btf_datasec_resolve(depth: 1, type_id: 1, mode: RESOLVE_PTR) = -22

The last invocation of btf_datasec_resolve should invoke btf_var_resolve
by means of env_stack_push, instead it returns EINVAL. The reason is that
env_stack_push is never executed for the second VAR.

    if (!env_type_is_resolve_sink(env, var_type) &amp;&amp;
        !env_type_is_resolved(env, var_type_id)) {
        env_stack_set_next_member(env, i + 1);
        return env_stack_push(env, var_type, var_type_id);
    }

env_type_is_resolve_sink() changes its behaviour based on resolve_mode.
For RESOLVE_PTR, we can simplify the if condition to the following:

    (btf_type_is_modifier() || btf_type_is_ptr) &amp;&amp; !env_type_is_resolved()

Since we're dealing with a VAR the clause evaluates to false. This is
not sufficient to trigger the bug however. The log output and EINVAL
are only generated if btf_type_id_size() fails.

    if (!btf_type_id_size(btf, &amp;type_id, &amp;type_size)) {
        btf_verifier_log_vsi(env, v-&gt;t, vsi, "Invalid type");
        return -EINVAL;
    }

Most types are sized, so for example a VAR referring to an INT is not a
problem. The bug is only triggered if a VAR points at a modifier. Since
we skipped btf_var_resolve that modifier was also never resolved, which
means that btf_resolved_type_id returns 0 aka VOID for the modifier.
This in turn causes btf_type_id_size to return NULL, triggering EINVAL.

To summarise, the following conditions are necessary:

- VAR pointing at PTR, STRUCT, UNION or ARRAY
- Followed by a VAR pointing at TYPEDEF, VOLATILE, CONST, RESTRICT or
  TYPE_TAG

The fix is to reset resolve_mode to RESOLVE_TBD before attempting to
resolve a VAR from a DATASEC.

Fixes: 1dc92851849c ("bpf: kernel side support for BTF Var and DataSec")
Signed-off-by: Lorenz Bauer &lt;lmb@isovalent.com&gt;
Link: https://lore.kernel.org/r/20230306112138.155352-2-lmb@isovalent.com
Signed-off-by: Martin KaFai Lau &lt;martin.lau@kernel.org&gt;
</content>
</entry>
<entry>
<title>Merge tag 'mm-stable-2023-02-20-13-37' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm</title>
<updated>2023-02-24T01:09:35Z</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2023-02-24T01:09:35Z</published>
<link rel='alternate' type='text/html' href='https://git.shady.money/linux/commit/?id=3822a7c40997dc86b1458766a3f146d62393f084'/>
<id>urn:sha1:3822a7c40997dc86b1458766a3f146d62393f084</id>
<content type='text'>
Pull MM updates from Andrew Morton:

 - Daniel Verkamp has contributed a memfd series ("mm/memfd: add
   F_SEAL_EXEC") which permits the setting of the memfd execute bit at
   memfd creation time, with the option of sealing the state of the X
   bit.

 - Peter Xu adds a patch series ("mm/hugetlb: Make huge_pte_offset()
   thread-safe for pmd unshare") which addresses a rare race condition
   related to PMD unsharing.

 - Several folioification patch serieses from Matthew Wilcox, Vishal
   Moola, Sidhartha Kumar and Lorenzo Stoakes

 - Johannes Weiner has a series ("mm: push down lock_page_memcg()")
   which does perform some memcg maintenance and cleanup work.

 - SeongJae Park has added DAMOS filtering to DAMON, with the series
   "mm/damon/core: implement damos filter".

   These filters provide users with finer-grained control over DAMOS's
   actions. SeongJae has also done some DAMON cleanup work.

 - Kairui Song adds a series ("Clean up and fixes for swap").

 - Vernon Yang contributed the series "Clean up and refinement for maple
   tree".

 - Yu Zhao has contributed the "mm: multi-gen LRU: memcg LRU" series. It
   adds to MGLRU an LRU of memcgs, to improve the scalability of global
   reclaim.

 - David Hildenbrand has added some userfaultfd cleanup work in the
   series "mm: uffd-wp + change_protection() cleanups".

 - Christoph Hellwig has removed the generic_writepages() library
   function in the series "remove generic_writepages".

 - Baolin Wang has performed some maintenance on the compaction code in
   his series "Some small improvements for compaction".

 - Sidhartha Kumar is doing some maintenance work on struct page in his
   series "Get rid of tail page fields".

 - David Hildenbrand contributed some cleanup, bugfixing and
   generalization of pte management and of pte debugging in his series
   "mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE on all architectures with
   swap PTEs".

 - Mel Gorman and Neil Brown have removed the __GFP_ATOMIC allocation
   flag in the series "Discard __GFP_ATOMIC".

 - Sergey Senozhatsky has improved zsmalloc's memory utilization with
   his series "zsmalloc: make zspage chain size configurable".

 - Joey Gouly has added prctl() support for prohibiting the creation of
   writeable+executable mappings.

   The previous BPF-based approach had shortcomings. See "mm: In-kernel
   support for memory-deny-write-execute (MDWE)".

 - Waiman Long did some kmemleak cleanup and bugfixing in the series
   "mm/kmemleak: Simplify kmemleak_cond_resched() &amp; fix UAF".

 - T.J. Alumbaugh has contributed some MGLRU cleanup work in his series
   "mm: multi-gen LRU: improve".

 - Jiaqi Yan has provided some enhancements to our memory error
   statistics reporting, mainly by presenting the statistics on a
   per-node basis. See the series "Introduce per NUMA node memory error
   statistics".

 - Mel Gorman has a second and hopefully final shot at fixing a CPU-hog
   regression in compaction via his series "Fix excessive CPU usage
   during compaction".

 - Christoph Hellwig does some vmalloc maintenance work in the series
   "cleanup vfree and vunmap".

 - Christoph Hellwig has removed block_device_operations.rw_page() in
   ths series "remove -&gt;rw_page".

 - We get some maple_tree improvements and cleanups in Liam Howlett's
   series "VMA tree type safety and remove __vma_adjust()".

 - Suren Baghdasaryan has done some work on the maintainability of our
   vm_flags handling in the series "introduce vm_flags modifier
   functions".

 - Some pagemap cleanup and generalization work in Mike Rapoport's
   series "mm, arch: add generic implementation of pfn_valid() for
   FLATMEM" and "fixups for generic implementation of pfn_valid()"

 - Baoquan He has done some work to make /proc/vmallocinfo and
   /proc/kcore better represent the real state of things in his series
   "mm/vmalloc.c: allow vread() to read out vm_map_ram areas".

 - Jason Gunthorpe rationalized the GUP system's interface to the rest
   of the kernel in the series "Simplify the external interface for
   GUP".

 - SeongJae Park wishes to migrate people from DAMON's debugfs interface
   over to its sysfs interface. To support this, we'll temporarily be
   printing warnings when people use the debugfs interface. See the
   series "mm/damon: deprecate DAMON debugfs interface".

 - Andrey Konovalov provided the accurately named "lib/stackdepot: fixes
   and clean-ups" series.

 - Huang Ying has provided a dramatic reduction in migration's TLB flush
   IPI rates with the series "migrate_pages(): batch TLB flushing".

 - Arnd Bergmann has some objtool fixups in "objtool warning fixes".

* tag 'mm-stable-2023-02-20-13-37' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (505 commits)
  include/linux/migrate.h: remove unneeded externs
  mm/memory_hotplug: cleanup return value handing in do_migrate_range()
  mm/uffd: fix comment in handling pte markers
  mm: change to return bool for isolate_movable_page()
  mm: hugetlb: change to return bool for isolate_hugetlb()
  mm: change to return bool for isolate_lru_page()
  mm: change to return bool for folio_isolate_lru()
  objtool: add UACCESS exceptions for __tsan_volatile_read/write
  kmsan: disable ftrace in kmsan core code
  kasan: mark addr_has_metadata __always_inline
  mm: memcontrol: rename memcg_kmem_enabled()
  sh: initialize max_mapnr
  m68k/nommu: add missing definition of ARCH_PFN_OFFSET
  mm: percpu: fix incorrect size in pcpu_obj_full_size()
  maple_tree: reduce stack usage with gcc-9 and earlier
  mm: page_alloc: call panic() when memoryless node allocation fails
  mm: multi-gen LRU: avoid futile retries
  migrate_pages: move THP/hugetlb migration support check to simplify code
  migrate_pages: batch flushing TLB
  migrate_pages: share more code between _unmap and _move
  ...
</content>
</entry>
<entry>
<title>bpf: Allow reads from uninit stack</title>
<updated>2023-02-22T20:34:50Z</updated>
<author>
<name>Eduard Zingerman</name>
<email>eddyz87@gmail.com</email>
</author>
<published>2023-02-19T20:04:26Z</published>
<link rel='alternate' type='text/html' href='https://git.shady.money/linux/commit/?id=6715df8d5d24655b9fd368e904028112b54c7de1'/>
<id>urn:sha1:6715df8d5d24655b9fd368e904028112b54c7de1</id>
<content type='text'>
This commits updates the following functions to allow reads from
uninitialized stack locations when env-&gt;allow_uninit_stack option is
enabled:
- check_stack_read_fixed_off()
- check_stack_range_initialized(), called from:
  - check_stack_read_var_off()
  - check_helper_mem_access()

Such change allows to relax logic in stacksafe() to treat STACK_MISC
and STACK_INVALID in a same way and make the following stack slot
configurations equivalent:

  |  Cached state    |  Current state   |
  |   stack slot     |   stack slot     |
  |------------------+------------------|
  | STACK_INVALID or | STACK_INVALID or |
  | STACK_MISC       | STACK_SPILL   or |
  |                  | STACK_MISC    or |
  |                  | STACK_ZERO    or |
  |                  | STACK_DYNPTR     |

This leads to significant verification speed gains (see below).

The idea was suggested by Andrii Nakryiko [1] and initial patch was
created by Alexei Starovoitov [2].

Currently the env-&gt;allow_uninit_stack is allowed for programs loaded
by users with CAP_PERFMON or CAP_SYS_ADMIN capabilities.

A number of test cases from verifier/*.c were expecting uninitialized
stack access to be an error. These test cases were updated to execute
in unprivileged mode (thus preserving the tests).

The test progs/test_global_func10.c expected "invalid indirect read
from stack" error message because of the access to uninitialized
memory region. This error is no longer possible in privileged mode.
The test is updated to provoke an error "invalid indirect access to
stack" because of access to invalid stack address (such error is not
verified by progs/test_global_func*.c series of tests).

The following tests had to be removed because these can't be made
unprivileged:
- verifier/sock.c:
  - "sk_storage_get(map, skb-&gt;sk, &amp;stack_value, 1): partially init
  stack_value"
  BPF_PROG_TYPE_SCHED_CLS programs are not executed in unprivileged mode.
- verifier/var_off.c:
  - "indirect variable-offset stack access, max_off+size &gt; max_initialized"
  - "indirect variable-offset stack access, uninitialized"
  These tests verify that access to uninitialized stack values is
  detected when stack offset is not a constant. However, variable
  stack access is prohibited in unprivileged mode, thus these tests
  are no longer valid.

 * * *

Here is veristat log comparing this patch with current master on a
set of selftest binaries listed in tools/testing/selftests/bpf/veristat.cfg
and cilium BPF binaries (see [3]):

$ ./veristat -e file,prog,states -C -f 'states_pct&lt;-30' master.log current.log
File                        Program                     States (A)  States (B)  States    (DIFF)
--------------------------  --------------------------  ----------  ----------  ----------------
bpf_host.o                  tail_handle_ipv6_from_host         349         244    -105 (-30.09%)
bpf_host.o                  tail_handle_nat_fwd_ipv4          1320         895    -425 (-32.20%)
bpf_lxc.o                   tail_handle_nat_fwd_ipv4          1320         895    -425 (-32.20%)
bpf_sock.o                  cil_sock4_connect                   70          48     -22 (-31.43%)
bpf_sock.o                  cil_sock4_sendmsg                   68          46     -22 (-32.35%)
bpf_xdp.o                   tail_handle_nat_fwd_ipv4          1554         803    -751 (-48.33%)
bpf_xdp.o                   tail_lb_ipv4                      6457        2473   -3984 (-61.70%)
bpf_xdp.o                   tail_lb_ipv6                      7249        3908   -3341 (-46.09%)
pyperf600_bpf_loop.bpf.o    on_event                           287         145    -142 (-49.48%)
strobemeta.bpf.o            on_event                         15915        4772  -11143 (-70.02%)
strobemeta_nounroll2.bpf.o  on_event                         17087        3820  -13267 (-77.64%)
xdp_synproxy_kern.bpf.o     syncookie_tc                     21271        6635  -14636 (-68.81%)
xdp_synproxy_kern.bpf.o     syncookie_xdp                    23122        6024  -17098 (-73.95%)
--------------------------  --------------------------  ----------  ----------  ----------------

Note: I limited selection by states_pct&lt;-30%.

Inspection of differences in pyperf600_bpf_loop behavior shows that
the following patch for the test removes almost all differences:

    - a/tools/testing/selftests/bpf/progs/pyperf.h
    + b/tools/testing/selftests/bpf/progs/pyperf.h
    @ -266,8 +266,8 @ int __on_event(struct bpf_raw_tracepoint_args *ctx)
            }

            if (event-&gt;pthread_match || !pidData-&gt;use_tls) {
    -               void* frame_ptr;
    -               FrameData frame;
    +               void* frame_ptr = 0;
    +               FrameData frame = {};
                    Symbol sym = {};
                    int cur_cpu = bpf_get_smp_processor_id();

W/o this patch the difference comes from the following pattern
(for different variables):

    static bool get_frame_data(... FrameData *frame ...)
    {
        ...
        bpf_probe_read_user(&amp;frame-&gt;f_code, ...);
        if (!frame-&gt;f_code)
            return false;
        ...
        bpf_probe_read_user(&amp;frame-&gt;co_name, ...);
        if (frame-&gt;co_name)
            ...;
    }

    int __on_event(struct bpf_raw_tracepoint_args *ctx)
    {
        FrameData frame;
        ...
        get_frame_data(... &amp;frame ...) // indirectly via a bpf_loop &amp; callback
        ...
    }

    SEC("raw_tracepoint/kfree_skb")
    int on_event(struct bpf_raw_tracepoint_args* ctx)
    {
        ...
        ret |= __on_event(ctx);
        ret |= __on_event(ctx);
        ...
    }

With regards to value `frame-&gt;co_name` the following is important:
- Because of the conditional `if (!frame-&gt;f_code)` each call to
  __on_event() produces two states, one with `frame-&gt;co_name` marked
  as STACK_MISC, another with it as is (and marked STACK_INVALID on a
  first call).
- The call to bpf_probe_read_user() does not mark stack slots
  corresponding to `&amp;frame-&gt;co_name` as REG_LIVE_WRITTEN but it marks
  these slots as BPF_MISC, this happens because of the following loop
  in the check_helper_call():

	for (i = 0; i &lt; meta.access_size; i++) {
		err = check_mem_access(env, insn_idx, meta.regno, i, BPF_B,
				       BPF_WRITE, -1, false);
		if (err)
			return err;
	}

  Note the size of the write, it is a one byte write for each byte
  touched by a helper. The BPF_B write does not lead to write marks
  for the target stack slot.
- Which means that w/o this patch when second __on_event() call is
  verified `if (frame-&gt;co_name)` will propagate read marks first to a
  stack slot with STACK_MISC marks and second to a stack slot with
  STACK_INVALID marks and these states would be considered different.

[1] https://lore.kernel.org/bpf/CAEf4BzY3e+ZuC6HUa8dCiUovQRg2SzEk7M-dSkqNZyn=xEmnPA@mail.gmail.com/
[2] https://lore.kernel.org/bpf/CAADnVQKs2i1iuZ5SUGuJtxWVfGYR9kDgYKhq3rNV+kBLQCu7rA@mail.gmail.com/
[3] git@github.com:anakryiko/cilium.git

Suggested-by: Andrii Nakryiko &lt;andrii@kernel.org&gt;
Co-developed-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: Eduard Zingerman &lt;eddyz87@gmail.com&gt;
Acked-by: Andrii Nakryiko &lt;andrii@kernel.org&gt;
Link: https://lore.kernel.org/r/20230219200427.606541-2-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
</content>
</entry>
<entry>
<title>bpf: add missing header file include</title>
<updated>2023-02-22T17:52:32Z</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2023-02-22T17:52:32Z</published>
<link rel='alternate' type='text/html' href='https://git.shady.money/linux/commit/?id=f3dd0c53370e70c0f9b7e931bbec12916f3bb8cc'/>
<id>urn:sha1:f3dd0c53370e70c0f9b7e931bbec12916f3bb8cc</id>
<content type='text'>
Commit 74e19ef0ff80 ("uaccess: Add speculation barrier to
copy_from_user()") built fine on x86-64 and arm64, and that's the extent
of my local build testing.

It turns out those got the &lt;linux/nospec.h&gt; include incidentally through
other header files (&lt;linux/kvm_host.h&gt; in particular), but that was not
true of other architectures, resulting in build errors

  kernel/bpf/core.c: In function ‘___bpf_prog_run’:
  kernel/bpf/core.c:1913:3: error: implicit declaration of function ‘barrier_nospec’

so just make sure to explicitly include the proper &lt;linux/nospec.h&gt;
header file to make everybody see it.

Fixes: 74e19ef0ff80 ("uaccess: Add speculation barrier to copy_from_user()")
Reported-by: kernel test robot &lt;lkp@intel.com&gt;
Reported-by: Viresh Kumar &lt;viresh.kumar@linaro.org&gt;
Reported-by: Huacai Chen &lt;chenhuacai@loongson.cn&gt;
Tested-by: Geert Uytterhoeven &lt;geert@linux-m68k.org&gt;
Tested-by: Dave Hansen &lt;dave.hansen@linux.intel.com&gt;
Acked-by: Alexei Starovoitov &lt;alexei.starovoitov@gmail.com&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
</entry>
<entry>
<title>Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next</title>
<updated>2023-02-22T02:24:12Z</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2023-02-22T02:24:12Z</published>
<link rel='alternate' type='text/html' href='https://git.shady.money/linux/commit/?id=5b7c4cabbb65f5c469464da6c5f614cbd7f730f2'/>
<id>urn:sha1:5b7c4cabbb65f5c469464da6c5f614cbd7f730f2</id>
<content type='text'>
Pull networking updates from Jakub Kicinski:
 "Core:

   - Add dedicated kmem_cache for typical/small skb-&gt;head, avoid having
     to access struct page at kfree time, and improve memory use.

   - Introduce sysctl to set default RPS configuration for new netdevs.

   - Define Netlink protocol specification format which can be used to
     describe messages used by each family and auto-generate parsers.
     Add tools for generating kernel data structures and uAPI headers.

   - Expose all net/core sysctls inside netns.

   - Remove 4s sleep in netpoll if carrier is instantly detected on
     boot.

   - Add configurable limit of MDB entries per port, and port-vlan.

   - Continue populating drop reasons throughout the stack.

   - Retire a handful of legacy Qdiscs and classifiers.

  Protocols:

   - Support IPv4 big TCP (TSO frames larger than 64kB).

   - Add IP_LOCAL_PORT_RANGE socket option, to control local port range
     on socket by socket basis.

   - Track and report in procfs number of MPTCP sockets used.

   - Support mixing IPv4 and IPv6 flows in the in-kernel MPTCP path
     manager.

   - IPv6: don't check net.ipv6.route.max_size and rely on garbage
     collection to free memory (similarly to IPv4).

   - Support Penultimate Segment Pop (PSP) flavor in SRv6 (RFC8986).

   - ICMP: add per-rate limit counters.

   - Add support for user scanning requests in ieee802154.

   - Remove static WEP support.

   - Support minimal Wi-Fi 7 Extremely High Throughput (EHT) rate
     reporting.

   - WiFi 7 EHT channel puncturing support (client &amp; AP).

  BPF:

   - Add a rbtree data structure following the "next-gen data structure"
     precedent set by recently added linked list, that is, by using
     kfunc + kptr instead of adding a new BPF map type.

   - Expose XDP hints via kfuncs with initial support for RX hash and
     timestamp metadata.

   - Add BPF_F_NO_TUNNEL_KEY extension to bpf_skb_set_tunnel_key to
     better support decap on GRE tunnel devices not operating in collect
     metadata.

   - Improve x86 JIT's codegen for PROBE_MEM runtime error checks.

   - Remove the need for trace_printk_lock for bpf_trace_printk and
     bpf_trace_vprintk helpers.

   - Extend libbpf's bpf_tracing.h support for tracing arguments of
     kprobes/uprobes and syscall as a special case.

   - Significantly reduce the search time for module symbols by
     livepatch and BPF.

   - Enable cpumasks to be used as kptrs, which is useful for tracing
     programs tracking which tasks end up running on which CPUs in
     different time intervals.

   - Add support for BPF trampoline on s390x and riscv64.

   - Add capability to export the XDP features supported by the NIC.

   - Add __bpf_kfunc tag for marking kernel functions as kfuncs.

   - Add cgroup.memory=nobpf kernel parameter option to disable BPF
     memory accounting for container environments.

  Netfilter:

   - Remove the CLUSTERIP target. It has been marked as obsolete for
     years, and we still have WARN splats wrt races of the out-of-band
     /proc interface installed by this target.

   - Add 'destroy' commands to nf_tables. They are identical to the
     existing 'delete' commands, but do not return an error if the
     referenced object (set, chain, rule...) did not exist.

  Driver API:

   - Improve cpumask_local_spread() locality to help NICs set the right
     IRQ affinity on AMD platforms.

   - Separate C22 and C45 MDIO bus transactions more clearly.

   - Introduce new DCB table to control DSCP rewrite on egress.

   - Support configuration of Physical Layer Collision Avoidance (PLCA)
     Reconciliation Sublayer (RS) (802.3cg-2019). Modern version of
     shared medium Ethernet.

   - Support for MAC Merge layer (IEEE 802.3-2018 clause 99). Allowing
     preemption of low priority frames by high priority frames.

   - Add support for controlling MACSec offload using netlink SET.

   - Rework devlink instance refcounts to allow registration and
     de-registration under the instance lock. Split the code into
     multiple files, drop some of the unnecessarily granular locks and
     factor out common parts of netlink operation handling.

   - Add TX frame aggregation parameters (for USB drivers).

   - Add a new attr TCA_EXT_WARN_MSG to report TC (offload) warning
     messages with notifications for debug.

   - Allow offloading of UDP NEW connections via act_ct.

   - Add support for per action HW stats in TC.

   - Support hardware miss to TC action (continue processing in SW from
     a specific point in the action chain).

   - Warn if old Wireless Extension user space interface is used with
     modern cfg80211/mac80211 drivers. Do not support Wireless
     Extensions for Wi-Fi 7 devices at all. Everyone should switch to
     using nl80211 interface instead.

   - Improve the CAN bit timing configuration. Use extack to return
     error messages directly to user space, update the SJW handling,
     including the definition of a new default value that will benefit
     CAN-FD controllers, by increasing their oscillator tolerance.

  New hardware / drivers:

   - Ethernet:
      - nVidia BlueField-3 support (control traffic driver)
      - Ethernet support for imx93 SoCs
      - Motorcomm yt8531 gigabit Ethernet PHY
      - onsemi NCN26000 10BASE-T1S PHY (with support for PLCA)
      - Microchip LAN8841 PHY (incl. cable diagnostics and PTP)
      - Amlogic gxl MDIO mux

   - WiFi:
      - RealTek RTL8188EU (rtl8xxxu)
      - Qualcomm Wi-Fi 7 devices (ath12k)

   - CAN:
      - Renesas R-Car V4H

  Drivers:

   - Bluetooth:
      - Set Per Platform Antenna Gain (PPAG) for Intel controllers.

   - Ethernet NICs:
      - Intel (1G, igc):
         - support TSN / Qbv / packet scheduling features of i226 model
      - Intel (100G, ice):
         - use GNSS subsystem instead of TTY
         - multi-buffer XDP support
         - extend support for GPIO pins to E823 devices
      - nVidia/Mellanox:
         - update the shared buffer configuration on PFC commands
         - implement PTP adjphase function for HW offset control
         - TC support for Geneve and GRE with VF tunnel offload
         - more efficient crypto key management method
         - multi-port eswitch support
      - Netronome/Corigine:
         - add DCB IEEE support
         - support IPsec offloading for NFP3800
      - Freescale/NXP (enetc):
         - support XDP_REDIRECT for XDP non-linear buffers
         - improve reconfig, avoid link flap and waiting for idle
         - support MAC Merge layer
      - Other NICs:
         - sfc/ef100: add basic devlink support for ef100
         - ionic: rx_push mode operation (writing descriptors via MMIO)
         - bnxt: use the auxiliary bus abstraction for RDMA
         - r8169: disable ASPM and reset bus in case of tx timeout
         - cpsw: support QSGMII mode for J721e CPSW9G
         - cpts: support pulse-per-second output
         - ngbe: add an mdio bus driver
         - usbnet: optimize usbnet_bh() by avoiding unnecessary queuing
         - r8152: handle devices with FW with NCM support
         - amd-xgbe: support 10Mbps, 2.5GbE speeds and rx-adaptation
         - virtio-net: support multi buffer XDP
         - virtio/vsock: replace virtio_vsock_pkt with sk_buff
         - tsnep: XDP support

   - Ethernet high-speed switches:
      - nVidia/Mellanox (mlxsw):
         - add support for latency TLV (in FW control messages)
      - Microchip (sparx5):
         - separate explicit and implicit traffic forwarding rules, make
           the implicit rules always active
         - add support for egress DSCP rewrite
         - IS0 VCAP support (Ingress Classification)
         - IS2 VCAP filters (protos, L3 addrs, L4 ports, flags, ToS
           etc.)
         - ES2 VCAP support (Egress Access Control)
         - support for Per-Stream Filtering and Policing (802.1Q,
           8.6.5.1)

   - Ethernet embedded switches:
      - Marvell (mv88e6xxx):
         - add MAB (port auth) offload support
         - enable PTP receive for mv88e6390
      - NXP (ocelot):
         - support MAC Merge layer
         - support for the the vsc7512 internal copper phys
      - Microchip:
         - lan9303: convert to PHYLINK
         - lan966x: support TC flower filter statistics
         - lan937x: PTP support for KSZ9563/KSZ8563 and LAN937x
         - lan937x: support Credit Based Shaper configuration
         - ksz9477: support Energy Efficient Ethernet
      - other:
         - qca8k: convert to regmap read/write API, use bulk operations
         - rswitch: Improve TX timestamp accuracy

   - Intel WiFi (iwlwifi):
      - EHT (Wi-Fi 7) rate reporting
      - STEP equalizer support: transfer some STEP (connection to radio
        on platforms with integrated wifi) related parameters from the
        BIOS to the firmware.

   - Qualcomm 802.11ax WiFi (ath11k):
      - IPQ5018 support
      - Fine Timing Measurement (FTM) responder role support
      - channel 177 support

   - MediaTek WiFi (mt76):
      - per-PHY LED support
      - mt7996: EHT (Wi-Fi 7) support
      - Wireless Ethernet Dispatch (WED) reset support
      - switch to using page pool allocator

   - RealTek WiFi (rtw89):
      - support new version of Bluetooth co-existance

   - Mobile:
      - rmnet: support TX aggregation"

* tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1872 commits)
  page_pool: add a comment explaining the fragment counter usage
  net: ethtool: fix __ethtool_dev_mm_supported() implementation
  ethtool: pse-pd: Fix double word in comments
  xsk: add linux/vmalloc.h to xsk.c
  sefltests: netdevsim: wait for devlink instance after netns removal
  selftest: fib_tests: Always cleanup before exit
  net/mlx5e: Align IPsec ASO result memory to be as required by hardware
  net/mlx5e: TC, Set CT miss to the specific ct action instance
  net/mlx5e: Rename CHAIN_TO_REG to MAPPED_OBJ_TO_REG
  net/mlx5: Refactor tc miss handling to a single function
  net/mlx5: Kconfig: Make tc offload depend on tc skb extension
  net/sched: flower: Support hardware miss to tc action
  net/sched: flower: Move filter handle initialization earlier
  net/sched: cls_api: Support hardware miss to tc action
  net/sched: Rename user cookie and act cookie
  sfc: fix builds without CONFIG_RTC_LIB
  sfc: clean up some inconsistent indentings
  net/mlx4_en: Introduce flexible array to silence overflow warning
  net: lan966x: Fix possible deadlock inside PTP
  net/ulp: Remove redundant -&gt;clone() test in inet_clone_ulp().
  ...
</content>
</entry>
<entry>
<title>uaccess: Add speculation barrier to copy_from_user()</title>
<updated>2023-02-21T22:45:22Z</updated>
<author>
<name>Dave Hansen</name>
<email>dave.hansen@linux.intel.com</email>
</author>
<published>2023-02-21T20:30:15Z</published>
<link rel='alternate' type='text/html' href='https://git.shady.money/linux/commit/?id=74e19ef0ff8061ef55957c3abd71614ef0f42f47'/>
<id>urn:sha1:74e19ef0ff8061ef55957c3abd71614ef0f42f47</id>
<content type='text'>
The results of "access_ok()" can be mis-speculated.  The result is that
you can end speculatively:

	if (access_ok(from, size))
		// Right here

even for bad from/size combinations.  On first glance, it would be ideal
to just add a speculation barrier to "access_ok()" so that its results
can never be mis-speculated.

But there are lots of system calls just doing access_ok() via
"copy_to_user()" and friends (example: fstat() and friends).  Those are
generally not problematic because they do not _consume_ data from
userspace other than the pointer.  They are also very quick and common
system calls that should not be needlessly slowed down.

"copy_from_user()" on the other hand uses a user-controller pointer and
is frequently followed up with code that might affect caches.  Take
something like this:

	if (!copy_from_user(&amp;kernelvar, uptr, size))
		do_something_with(kernelvar);

If userspace passes in an evil 'uptr' that *actually* points to a kernel
addresses, and then do_something_with() has cache (or other)
side-effects, it could allow userspace to infer kernel data values.

Add a barrier to the common copy_from_user() code to prevent
mis-speculated values which happen after the copy.

Also add a stub for architectures that do not define barrier_nospec().
This makes the macro usable in generic code.

Since the barrier is now usable in generic code, the x86 #ifdef in the
BPF code can also go away.

Reported-by: Jordy Zomer &lt;jordyzomer@google.com&gt;
Suggested-by: Linus Torvalds &lt;torvalds@linuxfoundation.org&gt;
Signed-off-by: Dave Hansen &lt;dave.hansen@linux.intel.com&gt;
Reviewed-by: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Acked-by: Daniel Borkmann &lt;daniel@iogearbox.net&gt;   # BPF bits
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
</entry>
</feed>
