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Andrey Vagin 20afc60f89 x86, perf: Check that current->mm is alive before getting user callchain 
An event may occur when an mm is already released.

I added an event in dequeue_entity() and caught a panic with
the following backtrace:

[  434.421110] BUG: unable to handle kernel NULL pointer dereference at 0000000000000050
[  434.421258] IP: [<ffffffff810464ac>] __get_user_pages_fast+0x9c/0x120
...
[  434.421258] Call Trace:
[  434.421258]  [<ffffffff8101ae81>] copy_from_user_nmi+0x51/0xf0
[  434.421258]  [<ffffffff8109a0d5>] ? sched_clock_local+0x25/0x90
[  434.421258]  [<ffffffff8101b048>] perf_callchain_user+0x128/0x170
[  434.421258]  [<ffffffff811154cd>] ? __perf_event_header__init_id+0xed/0x100
[  434.421258]  [<ffffffff81116690>] perf_prepare_sample+0x200/0x280
[  434.421258]  [<ffffffff81118da8>] __perf_event_overflow+0x1b8/0x290
[  434.421258]  [<ffffffff81065240>] ? tg_shares_up+0x0/0x670
[  434.421258]  [<ffffffff8104fe1a>] ? walk_tg_tree+0x6a/0xb0
[  434.421258]  [<ffffffff81118f44>] perf_swevent_overflow+0xc4/0xf0
[  434.421258]  [<ffffffff81119150>] do_perf_sw_event+0x1e0/0x250
[  434.421258]  [<ffffffff81119204>] perf_tp_event+0x44/0x70
[  434.421258]  [<ffffffff8105701f>] ftrace_profile_sched_block+0xdf/0x110
[  434.421258]  [<ffffffff8106121d>] dequeue_entity+0x2ad/0x2d0
[  434.421258]  [<ffffffff810614ec>] dequeue_task_fair+0x1c/0x60
[  434.421258]  [<ffffffff8105818a>] dequeue_task+0x9a/0xb0
[  434.421258]  [<ffffffff810581e2>] deactivate_task+0x42/0xe0
[  434.421258]  [<ffffffff814bc019>] thread_return+0x191/0x808
[  434.421258]  [<ffffffff81098a44>] ? switch_task_namespaces+0x24/0x60
[  434.421258]  [<ffffffff8106f4c4>] do_exit+0x464/0x910
[  434.421258]  [<ffffffff8106f9c8>] do_group_exit+0x58/0xd0
[  434.421258]  [<ffffffff8106fa57>] sys_exit_group+0x17/0x20
[  434.421258]  [<ffffffff8100b202>] system_call_fastpath+0x16/0x1b

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: stable@kernel.org
Link: http://lkml.kernel.org/r/1314693156-24131-1-git-send-email-avagin@openvz.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-08-31 15:56:31 +02:00
..
alpha All Arch: remove linkage for sys_nfsservctl system call 2011-08-26 15:09:58 -07:00
arm Merge branch 'pm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm 2011-08-28 10:05:39 -07:00
avr32 All Arch: remove linkage for sys_nfsservctl system call 2011-08-26 15:09:58 -07:00
blackfin All Arch: remove linkage for sys_nfsservctl system call 2011-08-26 15:09:58 -07:00
cris All Arch: remove linkage for sys_nfsservctl system call 2011-08-26 15:09:58 -07:00
frv All Arch: remove linkage for sys_nfsservctl system call 2011-08-26 15:09:58 -07:00
h8300 All Arch: remove linkage for sys_nfsservctl system call 2011-08-26 15:09:58 -07:00
ia64 All Arch: remove linkage for sys_nfsservctl system call 2011-08-26 15:09:58 -07:00
m32r All Arch: remove linkage for sys_nfsservctl system call 2011-08-26 15:09:58 -07:00
m68k All Arch: remove linkage for sys_nfsservctl system call 2011-08-26 15:09:58 -07:00
microblaze All Arch: remove linkage for sys_nfsservctl system call 2011-08-26 15:09:58 -07:00
mips All Arch: remove linkage for sys_nfsservctl system call 2011-08-26 15:09:58 -07:00
mn10300 All Arch: remove linkage for sys_nfsservctl system call 2011-08-26 15:09:58 -07:00
openrisc OpenRISC: Miscellaneous 2011-07-22 18:46:41 +02:00
parisc Merge branch 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/parisc-2.6 2011-08-04 06:36:20 -10:00
powerpc arch/powerpc/sysdev/fsl_rio.c: correct IECSR register clear value 2011-08-25 18:51:06 -07:00
s390 All Arch: remove linkage for sys_nfsservctl system call 2011-08-26 15:09:58 -07:00
score modules: make arch's use default loader hooks 2011-07-24 22:06:04 +09:30
sh All Arch: remove linkage for sys_nfsservctl system call 2011-08-26 15:09:58 -07:00
sparc All Arch: remove linkage for sys_nfsservctl system call 2011-08-26 15:09:58 -07:00
tile Merge branch 'apei-release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-acpi-2.6 2011-08-03 21:53:27 -10:00
um ptrace: unify show_regs() prototype 2011-07-26 16:49:43 -07:00
unicore32 Merge branch 'linux-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jbarnes/pci-2.6 2011-07-29 23:35:05 -07:00
x86 x86, perf: Check that current->mm is alive before getting user callchain 2011-08-31 15:56:31 +02:00
xtensa All Arch: remove linkage for sys_nfsservctl system call 2011-08-26 15:09:58 -07:00
.gitignore
Kconfig Add Kconfig option ARCH_HAVE_NMI_SAFE_CMPXCHG 2011-08-03 11:12:37 -04:00