linux/net/core/stream.c, branch v6.3

net: Remove WARN_ON_ONCE(sk->sk_forward_alloc) from sk_stream_kill_queues().

2023-02-11T03:53:42Z

Christoph Paasch reported that commit b5fc29233d28 ("inet6: Remove inet6_destroy_sock() in sk->sk_prot->destroy().") started triggering WARN_ON_ONCE(sk->sk_forward_alloc) in sk_stream_kill_queues(). [0 - 2] Also, we can reproduce it by a program in [3]. In the commit, we delay freeing ipv6_pinfo.pktoptions from sk->destroy() to sk->sk_destruct(), so sk->sk_forward_alloc is no longer zero in inet_csk_destroy_sock(). The same check has been in inet_sock_destruct() from at least v2.6, we can just remove the WARN_ON_ONCE(). However, among the users of sk_stream_kill_queues(), only CAIF is not calling inet_sock_destruct(). Thus, we add the same WARN_ON_ONCE() to caif_sock_destructor(). [0]: https://lore.kernel.org/netdev/39725AB4-88F1-41B3-B07F-949C5CAEFF4F@icloud.com/ [1]: https://github.com/multipath-tcp/mptcp_net-next/issues/341 [2]: WARNING: CPU: 0 PID: 3232 at net/core/stream.c:212 sk_stream_kill_queues+0x2f9/0x3e0 Modules linked in: CPU: 0 PID: 3232 Comm: syz-executor.0 Not tainted 6.2.0-rc5ab24eb4698afbe147b424149c529e2a43ec24eb5 #2 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 RIP: 0010:sk_stream_kill_queues+0x2f9/0x3e0 Code: 03 0f b6 04 02 84 c0 74 08 3c 03 0f 8e ec 00 00 00 8b ab 08 01 00 00 e9 60 ff ff ff e8 d0 5f b6 fe 0f 0b eb 97 e8 c7 5f b6 fe <0f> 0b eb a0 e8 be 5f b6 fe 0f 0b e9 6a fe ff ff e8 02 07 e3 fe e9 RSP: 0018:ffff88810570fc68 EFLAGS: 00010293 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: ffff888101f38f40 RSI: ffffffff8285e529 RDI: 0000000000000005 RBP: 0000000000000ce0 R08: 0000000000000005 R09: 0000000000000000 R10: 0000000000000ce0 R11: 0000000000000001 R12: ffff8881009e9488 R13: ffffffff84af2cc0 R14: 0000000000000000 R15: ffff8881009e9458 FS: 00007f7fdfbd5800(0000) GS:ffff88811b600000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000001b32923000 CR3: 00000001062fc006 CR4: 0000000000170ef0 Call Trace: inet_csk_destroy_sock+0x1a1/0x320 __tcp_close+0xab6/0xe90 tcp_close+0x30/0xc0 inet_release+0xe9/0x1f0 inet6_release+0x4c/0x70 __sock_release+0xd2/0x280 sock_close+0x15/0x20 __fput+0x252/0xa20 task_work_run+0x169/0x250 exit_to_user_mode_prepare+0x113/0x120 syscall_exit_to_user_mode+0x1d/0x40 do_syscall_64+0x48/0x90 entry_SYSCALL_64_after_hwframe+0x72/0xdc RIP: 0033:0x7f7fdf7ae28d Code: c1 20 00 00 75 10 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 ee fb ff ff 48 89 04 24 b8 03 00 00 00 0f 05 <48> 8b 3c 24 48 89 c2 e8 37 fc ff ff 48 89 d0 48 83 c4 08 48 3d 01 RSP: 002b:00000000007dfbb0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000004 RCX: 00007f7fdf7ae28d RDX: 0000000000000000 RSI: ffffffffffffffff RDI: 0000000000000003 RBP: 0000000000000000 R08: 000000007f338e0f R09: 0000000000000e0f R10: 000000007f338e13 R11: 0000000000000293 R12: 00007f7fdefff000 R13: 00007f7fdefffcd8 R14: 00007f7fdefffce0 R15: 00007f7fdefffcd8 [3]: https://lore.kernel.org/netdev/20230208004245.83497-1-kuniyu@amazon.com/ Fixes: b5fc29233d28 ("inet6: Remove inet6_destroy_sock() in sk->sk_prot->destroy().") Reported-by: syzbot Reported-by: Christoph Paasch Signed-off-by: Kuniyuki Iwashima Reviewed-by: Eric Dumazet Signed-off-by: Jakub Kicinski

net: stream: purge sk_error_queue in sk_stream_kill_queues()

2022-12-19T12:33:16Z

Changheon Lee reported TCP socket leaks, with a nice repro. It seems we leak TCP sockets with the following sequence: 1) SOF_TIMESTAMPING_TX_ACK is enabled on the socket. Each ACK will cook an skb put in error queue, from __skb_tstamp_tx(). __skb_tstamp_tx() is using skb_clone(), unless SOF_TIMESTAMPING_OPT_TSONLY was also requested. 2) If the application is also using MSG_ZEROCOPY, then we put in the error queue cloned skbs that had a struct ubuf_info attached to them. Whenever an struct ubuf_info is allocated, sock_zerocopy_alloc() does a sock_hold(). As long as the cloned skbs are still in sk_error_queue, socket refcount is kept elevated. 3) Application closes the socket, while error queue is not empty. Since tcp_close() no longer purges the socket error queue, we might end up with a TCP socket with at least one skb in error queue keeping the socket alive forever. This bug can be (ab)used to consume all kernel memory and freeze the host. We need to purge the error queue, with proper synchronization against concurrent writers. Fixes: 24bcbe1cc69f ("net: stream: don't purge sk_error_queue in sk_stream_kill_queues()") Reported-by: Changheon Lee Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

treewide: use get_random_u32_below() instead of deprecated function

2022-11-18T01:15:15Z

This is a simple mechanical transformation done by: @@ expression E; @@ - prandom_u32_max + get_random_u32_below (E) Reviewed-by: Kees Cook Reviewed-by: Greg Kroah-Hartman Acked-by: Darrick J. Wong # for xfs Reviewed-by: SeongJae Park # for damon Reviewed-by: Jason Gunthorpe # for infiniband Reviewed-by: Russell King (Oracle) # for arm Acked-by: Ulf Hansson # for mmc Signed-off-by: Jason A. Donenfeld

treewide: use prandom_u32_max() when possible, part 1

2022-10-11T23:42:55Z

Rather than incurring a division or requesting too many random bytes for the given range, use the prandom_u32_max() function, which only takes the minimum required bytes from the RNG and avoids divisions. This was done mechanically with this coccinelle script: @basic@ expression E; type T; identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32"; typedef u64; @@ ( - ((T)get_random_u32() % (E)) + prandom_u32_max(E) | - ((T)get_random_u32() & ((E) - 1)) + prandom_u32_max(E * XXX_MAKE_SURE_E_IS_POW2) | - ((u64)(E) * get_random_u32() >> 32) + prandom_u32_max(E) | - ((T)get_random_u32() & ~PAGE_MASK) + prandom_u32_max(PAGE_SIZE) ) @multi_line@ identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32"; identifier RAND; expression E; @@ - RAND = get_random_u32(); ... when != RAND - RAND %= (E); + RAND = prandom_u32_max(E); // Find a potential literal @literal_mask@ expression LITERAL; type T; identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32"; position p; @@ ((T)get_random_u32()@p & (LITERAL)) // Add one to the literal. @script:python add_one@ literal << literal_mask.LITERAL; RESULT; @@ value = None if literal.startswith('0x'): value = int(literal, 16) elif literal[0] in '123456789': value = int(literal, 10) if value is None: print("I don't know how to handle %s" % (literal)) cocci.include_match(False) elif value == 2**32 - 1 or value == 2**31 - 1 or value == 2**24 - 1 or value == 2**16 - 1 or value == 2**8 - 1: print("Skipping 0x%x for cleanup elsewhere" % (value)) cocci.include_match(False) elif value & (value + 1) != 0: print("Skipping 0x%x because it's not a power of two minus one" % (value)) cocci.include_match(False) elif literal.startswith('0x'): coccinelle.RESULT = cocci.make_expr("0x%x" % (value + 1)) else: coccinelle.RESULT = cocci.make_expr("%d" % (value + 1)) // Replace the literal mask with the calculated result. @plus_one@ expression literal_mask.LITERAL; position literal_mask.p; expression add_one.RESULT; identifier FUNC; @@ - (FUNC()@p & (LITERAL)) + prandom_u32_max(RESULT) @collapse_ret@ type T; identifier VAR; expression E; @@ { - T VAR; - VAR = (E); - return VAR; + return E; } @drop_var@ type T; identifier VAR; @@ { - T VAR; ... when != VAR } Reviewed-by: Greg Kroah-Hartman Reviewed-by: Kees Cook Reviewed-by: Yury Norov Reviewed-by: KP Singh Reviewed-by: Jan Kara # for ext4 and sbitmap Reviewed-by: Christoph Böhmwalder # for drbd Acked-by: Jakub Kicinski Acked-by: Heiko Carstens # for s390 Acked-by: Ulf Hansson # for mmc Acked-by: Darrick J. Wong # for xfs Signed-off-by: Jason A. Donenfeld

net: If sock is dead don't access sock's sk_wq in sk_stream_wait_memory

2022-09-26T15:43:43Z

Fixes the below NULL pointer dereference: [...] [ 14.471200] Call Trace: [ 14.471562] [ 14.471882] lock_acquire+0x245/0x2e0 [ 14.472416] ? remove_wait_queue+0x12/0x50 [ 14.473014] ? _raw_spin_lock_irqsave+0x17/0x50 [ 14.473681] _raw_spin_lock_irqsave+0x3d/0x50 [ 14.474318] ? remove_wait_queue+0x12/0x50 [ 14.474907] remove_wait_queue+0x12/0x50 [ 14.475480] sk_stream_wait_memory+0x20d/0x340 [ 14.476127] ? do_wait_intr_irq+0x80/0x80 [ 14.476704] do_tcp_sendpages+0x287/0x600 [ 14.477283] tcp_bpf_push+0xab/0x260 [ 14.477817] tcp_bpf_sendmsg_redir+0x297/0x500 [ 14.478461] ? __local_bh_enable_ip+0x77/0xe0 [ 14.479096] tcp_bpf_send_verdict+0x105/0x470 [ 14.479729] tcp_bpf_sendmsg+0x318/0x4f0 [ 14.480311] sock_sendmsg+0x2d/0x40 [ 14.480822] ____sys_sendmsg+0x1b4/0x1c0 [ 14.481390] ? copy_msghdr_from_user+0x62/0x80 [ 14.482048] ___sys_sendmsg+0x78/0xb0 [ 14.482580] ? vmf_insert_pfn_prot+0x91/0x150 [ 14.483215] ? __do_fault+0x2a/0x1a0 [ 14.483738] ? do_fault+0x15e/0x5d0 [ 14.484246] ? __handle_mm_fault+0x56b/0x1040 [ 14.484874] ? lock_is_held_type+0xdf/0x130 [ 14.485474] ? find_held_lock+0x2d/0x90 [ 14.486046] ? __sys_sendmsg+0x41/0x70 [ 14.486587] __sys_sendmsg+0x41/0x70 [ 14.487105] ? intel_pmu_drain_pebs_core+0x350/0x350 [ 14.487822] do_syscall_64+0x34/0x80 [ 14.488345] entry_SYSCALL_64_after_hwframe+0x63/0xcd [...] The test scenario has the following flow: thread1 thread2 ----------- --------------- tcp_bpf_sendmsg tcp_bpf_send_verdict tcp_bpf_sendmsg_redir sock_close tcp_bpf_push_locked __sock_release tcp_bpf_push //inet_release do_tcp_sendpages sock->ops->release sk_stream_wait_memory // tcp_close sk_wait_event sk->sk_prot->close release_sock(__sk); *** lock_sock(sk); __tcp_close sock_orphan(sk) sk->sk_wq = NULL release_sock **** lock_sock(__sk); remove_wait_queue(sk_sleep(sk), &wait); sk_sleep(sk) //NULL pointer dereference &rcu_dereference_raw(sk->sk_wq)->wait While waiting for memory in thread1, the socket is released with its wait queue because thread2 has closed it. This caused by tcp_bpf_send_verdict didn't increase the f_count of psock->sk_redir->sk_socket->file in thread1. We should check if SOCK_DEAD flag is set on wakeup in sk_stream_wait_memory before accessing the wait queue. Suggested-by: Jakub Sitnicki Signed-off-by: Liu Jian Signed-off-by: Daniel Borkmann Acked-by: John Fastabend Cc: Eric Dumazet Link: https://lore.kernel.org/bpf/20220823133755.314697-2-liujian56@huawei.com

net: use WARN_ON_ONCE() in sk_stream_kill_queues()

2022-06-10T04:53:55Z

sk_stream_kill_queues() has three checks which have been useful to detect kernel bugs in the past. However they are potentially a problem because they could flood the syslog. Signed-off-by: Eric Dumazet Signed-off-by: Jakub Kicinski

net: stream: don't purge sk_error_queue in sk_stream_kill_queues()

2021-10-16T08:06:09Z

sk_stream_kill_queues() can be called on close when there are still outstanding skbs to transmit. Those skbs may try to queue notifications to the error queue (e.g. timestamps). If sk_stream_kill_queues() purges the queue without taking its lock the queue may get corrupted, and skbs leaked. This shows up as a warning about an rmem leak: WARNING: CPU: 24 PID: 0 at net/ipv4/af_inet.c:154 inet_sock_destruct+0x... The leak is always a multiple of 0x300 bytes (the value is in %rax on my builds, so RAX: 0000000000000300). 0x300 is truesize of an empty sk_buff. Indeed if we dump the socket state at the time of the warning the sk_error_queue is often (but not always) corrupted. The ->next pointer points back at the list head, but not the ->prev pointer. Indeed we can find the leaked skb by scanning the kernel memory for something that looks like an skb with ->sk = socket in question, and ->truesize = 0x300. The contents of ->cb[] of the skb confirms the suspicion that it is indeed a timestamp notification (as generated in __skb_complete_tx_timestamp()). Removing purging of sk_error_queue should be okay, since inet_sock_destruct() does it again once all socket refs are gone. Eric suggests this may cause sockets that go thru disconnect() to maintain notifications from the previous incarnations of the socket, but that should be okay since the race was there anyway, and disconnect() is not exactly dependable. Thanks to Jonathan Lemon and Omar Sandoval for help at various stages of tracing the issue. Fixes: cb9eff097831 ("net: new user space API for time stamping of incoming and outgoing packets") Signed-off-by: Jakub Kicinski Reviewed-by: Eric Dumazet Signed-off-by: David S. Miller

net: add new socket option SO_RESERVE_MEM

2021-09-30T12:36:46Z

This socket option provides a mechanism for users to reserve a certain amount of memory for the socket to use. When this option is set, kernel charges the user specified amount of memory to memcg, as well as sk_forward_alloc. This amount of memory is not reclaimable and is available in sk_forward_alloc for this socket. With this socket option set, the networking stack spends less cycles doing forward alloc and reclaim, which should lead to better system performance, with the cost of an amount of pre-allocated and unreclaimable memory, even under memory pressure. Note: This socket option is only available when memory cgroup is enabled and we require this reserved memory to be charged to the user's memcg. We hope this could avoid mis-behaving users to abused this feature to reserve a large amount on certain sockets and cause unfairness for others. Signed-off-by: Wei Wang Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

tcp: make sure EPOLLOUT wont be missed

2019-08-19T20:07:43Z

As Jason Baron explained in commit 790ba4566c1a ("tcp: set SOCK_NOSPACE under memory pressure"), it is crucial we properly set SOCK_NOSPACE when needed. However, Jason patch had a bug, because the 'nonblocking' status as far as sk_stream_wait_memory() is concerned is governed by MSG_DONTWAIT flag passed at sendmsg() time : long timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT); So it is very possible that tcp sendmsg() calls sk_stream_wait_memory(), and that sk_stream_wait_memory() returns -EAGAIN with SOCK_NOSPACE cleared, if sk->sk_sndtimeo has been set to a small (but not zero) value. This patch removes the 'noblock' variable since we must always set SOCK_NOSPACE if -EAGAIN is returned. It also renames the do_nonblock label since we might reach this code path even if we were in blocking mode. Fixes: 790ba4566c1a ("tcp: set SOCK_NOSPACE under memory pressure") Signed-off-by: Eric Dumazet Cc: Jason Baron Reported-by: Vladimir Rutsky Acked-by: Soheil Hassas Yeganeh Acked-by: Neal Cardwell Acked-by: Jason Baron Signed-off-by: David S. Miller

tcp: reduce POLLOUT events caused by TCP_NOTSENT_LOWAT

2018-12-05T05:21:18Z

TCP_NOTSENT_LOWAT socket option or sysctl was added in linux-3.12 as a step to enable bigger tcp sndbuf limits. It works reasonably well, but the following happens : Once the limit is reached, TCP stack generates an [E]POLLOUT event for every incoming ACK packet. This causes a high number of context switches. This patch implements the strategy David Miller added in sock_def_write_space() : - If TCP socket has a notsent_lowat constraint of X bytes, allow sendmsg() to fill up to X bytes, but send [E]POLLOUT only if number of notsent bytes is below X/2 This considerably reduces TCP_NOTSENT_LOWAT overhead, while allowing to keep the pipe full. Tested: 100 ms RTT netem testbed between A and B, 100 concurrent TCP_STREAM A:/# cat /proc/sys/net/ipv4/tcp_wmem 4096 262144 64000000 A:/# super_netperf 100 -H B -l 1000 -- -K bbr & A:/# grep TCP /proc/net/sockstat TCP: inuse 203 orphan 0 tw 19 alloc 414 mem 1364904 # This is about 54 MB of memory per flow :/ A:/# vmstat 5 5 procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu----- r b swpd free buff cache si so bi bo in cs us sy id wa st 0 0 0 256220672 13532 694976 0 0 10 0 28 14 0 1 99 0 0 2 0 0 256320016 13532 698480 0 0 512 0 715901 5927 0 10 90 0 0 0 0 0 256197232 13532 700992 0 0 735 13 771161 5849 0 11 89 0 0 1 0 0 256233824 13532 703320 0 0 512 23 719650 6635 0 11 89 0 0 2 0 0 256226880 13532 705780 0 0 642 4 775650 6009 0 12 88 0 0 A:/# echo 2097152 >/proc/sys/net/ipv4/tcp_notsent_lowat A:/# grep TCP /proc/net/sockstat TCP: inuse 203 orphan 0 tw 19 alloc 414 mem 86411 # 3.5 MB per flow A:/# vmstat 5 5 # check that context switches have not inflated too much. procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu----- r b swpd free buff cache si so bi bo in cs us sy id wa st 2 0 0 260386512 13592 662148 0 0 10 0 17 14 0 1 99 0 0 0 0 0 260519680 13592 604184 0 0 512 13 726843 12424 0 10 90 0 0 1 1 0 260435424 13592 598360 0 0 512 25 764645 12925 0 10 90 0 0 1 0 0 260855392 13592 578380 0 0 512 7 722943 13624 0 11 88 0 0 1 0 0 260445008 13592 601176 0 0 614 34 772288 14317 0 10 90 0 0 Signed-off-by: Eric Dumazet Acked-by: Soheil Hassas Yeganeh Signed-off-by: David S. Miller