linux/fs/proc/array.c, branch v2.6.37

CRED: Fix get_task_cred() and task_state() to not resurrect dead credentials

2010-07-29T22:16:17Z

It's possible for get_task_cred() as it currently stands to 'corrupt' a set of credentials by incrementing their usage count after their replacement by the task being accessed. What happens is that get_task_cred() can race with commit_creds(): TASK_1 TASK_2 RCU_CLEANER -->get_task_cred(TASK_2) rcu_read_lock() __cred = __task_cred(TASK_2) -->commit_creds() old_cred = TASK_2->real_cred TASK_2->real_cred = ... put_cred(old_cred) call_rcu(old_cred) [__cred->usage == 0] get_cred(__cred) [__cred->usage == 1] rcu_read_unlock() -->put_cred_rcu() [__cred->usage == 1] panic() However, since a tasks credentials are generally not changed very often, we can reasonably make use of a loop involving reading the creds pointer and using atomic_inc_not_zero() to attempt to increment it if it hasn't already hit zero. If successful, we can safely return the credentials in the knowledge that, even if the task we're accessing has released them, they haven't gone to the RCU cleanup code. We then change task_state() in procfs to use get_task_cred() rather than calling get_cred() on the result of __task_cred(), as that suffers from the same problem. Without this change, a BUG_ON in __put_cred() or in put_cred_rcu() can be tripped when it is noticed that the usage count is not zero as it ought to be, for example: kernel BUG at kernel/cred.c:168! invalid opcode: 0000 [#1] SMP last sysfs file: /sys/kernel/mm/ksm/run CPU 0 Pid: 2436, comm: master Not tainted 2.6.33.3-85.fc13.x86_64 #1 0HR330/OptiPlex 745 RIP: 0010:[] [] __put_cred+0xc/0x45 RSP: 0018:ffff88019e7e9eb8 EFLAGS: 00010202 RAX: 0000000000000001 RBX: ffff880161514480 RCX: 00000000ffffffff RDX: 00000000ffffffff RSI: ffff880140c690c0 RDI: ffff880140c690c0 RBP: ffff88019e7e9eb8 R08: 00000000000000d0 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000040 R12: ffff880140c690c0 R13: ffff88019e77aea0 R14: 00007fff336b0a5c R15: 0000000000000001 FS: 00007f12f50d97c0(0000) GS:ffff880007400000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f8f461bc000 CR3: 00000001b26ce000 CR4: 00000000000006f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Process master (pid: 2436, threadinfo ffff88019e7e8000, task ffff88019e77aea0) Stack: ffff88019e7e9ec8 ffffffff810698cd ffff88019e7e9ef8 ffffffff81069b45 <0> ffff880161514180 ffff880161514480 ffff880161514180 0000000000000000 <0> ffff88019e7e9f28 ffffffff8106aace 0000000000000001 0000000000000246 Call Trace: [] put_cred+0x13/0x15 [] commit_creds+0x16b/0x175 [] set_current_groups+0x47/0x4e [] sys_setgroups+0xf6/0x105 [] system_call_fastpath+0x16/0x1b Code: 48 8d 71 ff e8 7e 4e 15 00 85 c0 78 0b 8b 75 ec 48 89 df e8 ef 4a 15 00 48 83 c4 18 5b c9 c3 55 8b 07 8b 07 48 89 e5 85 c0 74 04 <0f> 0b eb fe 65 48 8b 04 25 00 cc 00 00 48 3b b8 58 04 00 00 75 RIP [] __put_cred+0xc/0x45 RSP ---[ end trace df391256a100ebdd ]--- Signed-off-by: David Howells Acked-by: Jiri Olsa Signed-off-by: Linus Torvalds

proc: get_nr_threads() doesn't need ->siglock any longer

2010-05-27T16:12:47Z

Now that task->signal can't go away get_nr_threads() doesn't need ->siglock to read signal->count. Also, make it inline, move into sched.h, and convert 2 other proc users of signal->count to use this (now trivial) helper. Henceforth get_nr_threads() is the only valid user of signal->count, we are ready to turn it into "int nr_threads" or, perhaps, kill it. Signed-off-by: Oleg Nesterov Cc: Alexey Dobriyan Cc: David Howells Cc: "Eric W. Biederman" Acked-by: Roland McGrath Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

revert "procfs: provide stack information for threads" and its fixup commits

2010-05-12T00:33:41Z

Originally, commit d899bf7b ("procfs: provide stack information for threads") attempted to introduce a new feature for showing where the threadstack was located and how many pages are being utilized by the stack. Commit c44972f1 ("procfs: disable per-task stack usage on NOMMU") was applied to fix the NO_MMU case. Commit 89240ba0 ("x86, fs: Fix x86 procfs stack information for threads on 64-bit") was applied to fix a bug in ia32 executables being loaded. Commit 9ebd4eba7 ("procfs: fix /proc//stat stack pointer for kernel threads") was applied to fix a bug which had kernel threads printing a userland stack address. Commit 1306d603f ('proc: partially revert "procfs: provide stack information for threads"') was then applied to revert the stack pages being used to solve a significant performance regression. This patch nearly undoes the effect of all these patches. The reason for reverting these is it provides an unusable value in field 28. For x86_64, a fork will result in the task->stack_start value being updated to the current user top of stack and not the stack start address. This unpredictability of the stack_start value makes it worthless. That includes the intended use of showing how much stack space a thread has. Other architectures will get different values. As an example, ia64 gets 0. The do_fork() and copy_process() functions appear to treat the stack_start and stack_size parameters as architecture specific. I only partially reverted c44972f1 ("procfs: disable per-task stack usage on NOMMU") . If I had completely reverted it, I would have had to change mm/Makefile only build pagewalk.o when CONFIG_PROC_PAGE_MONITOR is configured. Since I could not test the builds without significant effort, I decided to not change mm/Makefile. I only partially reverted 89240ba0 ("x86, fs: Fix x86 procfs stack information for threads on 64-bit") . I left the KSTK_ESP() change in place as that seemed worthwhile. Signed-off-by: Robin Holt Cc: Stefani Seibold Cc: KOSAKI Motohiro Cc: Michal Simek Cc: Ingo Molnar Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h

2010-03-30T13:02:32Z

percpu.h is included by sched.h and module.h and thus ends up being included when building most .c files. percpu.h includes slab.h which in turn includes gfp.h making everything defined by the two files universally available and complicating inclusion dependencies. percpu.h -> slab.h dependency is about to be removed. Prepare for this change by updating users of gfp and slab facilities include those headers directly instead of assuming availability. As this conversion needs to touch large number of source files, the following script is used as the basis of conversion. http://userweb.kernel.org/~tj/misc/slabh-sweep.py The script does the followings. * Scan files for gfp and slab usages and update includes such that only the necessary includes are there. ie. if only gfp is used, gfp.h, if slab is used, slab.h. * When the script inserts a new include, it looks at the include blocks and try to put the new include such that its order conforms to its surrounding. It's put in the include block which contains core kernel includes, in the same order that the rest are ordered - alphabetical, Christmas tree, rev-Xmas-tree or at the end if there doesn't seem to be any matching order. * If the script can't find a place to put a new include (mostly because the file doesn't have fitting include block), it prints out an error message indicating which .h file needs to be added to the file. The conversion was done in the following steps. 1. The initial automatic conversion of all .c files updated slightly over 4000 files, deleting around 700 includes and adding ~480 gfp.h and ~3000 slab.h inclusions. The script emitted errors for ~400 files. 2. Each error was manually checked. Some didn't need the inclusion, some needed manual addition while adding it to implementation .h or embedding .c file was more appropriate for others. This step added inclusions to around 150 files. 3. The script was run again and the output was compared to the edits from #2 to make sure no file was left behind. 4. Several build tests were done and a couple of problems were fixed. e.g. lib/decompress_*.c used malloc/free() wrappers around slab APIs requiring slab.h to be added manually. 5. The script was run on all .h files but without automatically editing them as sprinkling gfp.h and slab.h inclusions around .h files could easily lead to inclusion dependency hell. Most gfp.h inclusion directives were ignored as stuff from gfp.h was usually wildly available and often used in preprocessor macros. Each slab.h inclusion directive was examined and added manually as necessary. 6. percpu.h was updated not to include slab.h. 7. Build test were done on the following configurations and failures were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my distributed build env didn't work with gcov compiles) and a few more options had to be turned off depending on archs to make things build (like ipr on powerpc/64 which failed due to missing writeq). * x86 and x86_64 UP and SMP allmodconfig and a custom test config. * powerpc and powerpc64 SMP allmodconfig * sparc and sparc64 SMP allmodconfig * ia64 SMP allmodconfig * s390 SMP allmodconfig * alpha SMP allmodconfig * um on x86_64 SMP allmodconfig 8. percpu.h modifications were reverted so that it could be applied as a separate patch and serve as bisection point. Given the fact that I had only a couple of failures from tests on step 6, I'm fairly confident about the coverage of this conversion patch. If there is a breakage, it's likely to be something in one of the arch headers which should be easily discoverable easily on most builds of the specific arch. Signed-off-by: Tejun Heo Guess-its-ok-by: Christoph Lameter Cc: Ingo Molnar Cc: Lee Schermerhorn

fs: use rlimit helpers

2010-03-06T19:26:29Z

Make sure compiler won't do weird things with limits. E.g. fetching them twice may return 2 different values after writable limits are implemented. I.e. either use rlimit helpers added in commit 3e10e716abf3 ("resource: add helpers for fetching rlimits") or ACCESS_ONCE if not applicable. Signed-off-by: Jiri Slaby Cc: Alexander Viro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

vfs: Apply lockdep-based checking to rcu_dereference() uses

2010-02-25T09:34:48Z

Add lockdep-ified RCU primitives to alloc_fd(), files_fdtable() and fcheck_files(). Cc: Alexander Viro Signed-off-by: Paul E. McKenney Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com Cc: Alexander Viro LKML-Reference: <1266887105-1528-8-git-send-email-paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar

proc: partially revert "procfs: provide stack information for threads"

2010-01-11T17:34:06Z

Commit d899bf7b (procfs: provide stack information for threads) introduced to show stack information in /proc/{pid}/status. But it cause large performance regression. Unfortunately /proc/{pid}/status is used ps command too and ps is one of most important component. Because both to take mmap_sem and page table walk are heavily operation. If many process run, the ps performance is, [before d899bf7b] % perf stat ps >/dev/null Performance counter stats for 'ps': 4090.435806 task-clock-msecs # 0.032 CPUs 229 context-switches # 0.000 M/sec 0 CPU-migrations # 0.000 M/sec 234 page-faults # 0.000 M/sec 8587565207 cycles # 2099.425 M/sec 9866662403 instructions # 1.149 IPC 3789415411 cache-references # 926.409 M/sec 30419509 cache-misses # 7.437 M/sec 128.859521955 seconds time elapsed [after d899bf7b] % perf stat ps > /dev/null Performance counter stats for 'ps': 4305.081146 task-clock-msecs # 0.028 CPUs 480 context-switches # 0.000 M/sec 2 CPU-migrations # 0.000 M/sec 237 page-faults # 0.000 M/sec 9021211334 cycles # 2095.480 M/sec 10605887536 instructions # 1.176 IPC 3612650999 cache-references # 839.160 M/sec 23917502 cache-misses # 5.556 M/sec 152.277819582 seconds time elapsed Thus, this patch revert it. Fortunately /proc/{pid}/task/{tid}/smaps provide almost same information. we can use it. Commit d899bf7b introduced two features: 1) Add the annotattion of [thread stack: xxxx] mark to /proc/{pid}/task/{tid}/maps. 2) Add StackUsage field to /proc/{pid}/status. I only revert (2), because I haven't seen (1) cause regression. Signed-off-by: KOSAKI Motohiro Cc: Stefani Seibold Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Alexey Dobriyan Cc: "Eric W. Biederman" Cc: Randy Dunlap Cc: Andrew Morton Cc: Andi Kleen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

sched: Assert task state bits at build time

2009-12-17T12:22:45Z

Since everybody is lazy and prone to forgetting things, make the compiler help us a bit. Signed-off-by: Peter Zijlstra LKML-Reference: <20091217121830.060186433@chello.nl> Signed-off-by: Ingo Molnar

sched: Update task_state_arraypwith new states

2009-12-17T12:22:45Z

Neglected because its hidden... (who reads comments anyway) Signed-off-by: Peter Zijlstra LKML-Reference: <20091217121829.970166036@chello.nl> Signed-off-by: Ingo Molnar

Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

2009-12-05T23:30:49Z

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (35 commits) sched, cputime: Introduce thread_group_times() sched, cputime: Cleanups related to task_times() Revert "sched, x86: Optimize branch hint in __switch_to()" sched: Fix isolcpus boot option sched: Revert 498657a478c60be092208422fefa9c7b248729c2 sched, time: Define nsecs_to_jiffies() sched: Remove task_{u,s,g}time() sched: Introduce task_times() to replace task_{u,s}time() pair sched: Limit the number of scheduler debug messages sched.c: Call debug_show_all_locks() when dumping all tasks sched, x86: Optimize branch hint in __switch_to() sched: Optimize branch hint in context_switch() sched: Optimize branch hint in pick_next_task_fair() sched_feat_write(): Update ppos instead of file->f_pos sched: Sched_rt_periodic_timer vs cpu hotplug sched, kvm: Fix race condition involving sched_in_preempt_notifers sched: More generic WAKE_AFFINE vs select_idle_sibling() sched: Cleanup select_task_rq_fair() sched: Fix granularity of task_u/stime() sched: Fix/add missing update_rq_clock() calls ...