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x86, perf: Check that current->mm is alive before getting user callchain
author
Andrey Vagin
<avagin@openvz.org>
Tue, 30 Aug 2011 08:32:36 +0000
(12:32 +0400)
committer
Ingo Molnar
<mingo@elte.hu>
Wed, 31 Aug 2011 13:56:31 +0000
(15:56 +0200)
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>
arch/x86/kernel/cpu/perf_event.c
patch
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diff --git
a/arch/x86/kernel/cpu/perf_event.c
b/arch/x86/kernel/cpu/perf_event.c
index
4ee3abf
..
cfa62ec
100644
(file)
--- a/
arch/x86/kernel/cpu/perf_event.c
+++ b/
arch/x86/kernel/cpu/perf_event.c
@@
-1900,6
+1900,9
@@
perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs)
perf_callchain_store(entry, regs->ip);
+ if (!current->mm)
+ return;
+
if (perf_callchain_user32(regs, entry))
return;