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authorAndrey Vagin <avagin@openvz.org>2011-08-30 12:32:36 +0400
committerIngo Molnar <mingo@elte.hu>2011-08-31 15:56:31 +0200
commit20afc60f892d285fde179ead4b24e6a7938c2f1b (patch)
tree58f95af64093a9fed603a35e323cf5f134882c9c /arch/x86/kernel
parent7f310a5d4e8525ac0cc2f58c973d2100ce034410 (diff)
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>
Diffstat (limited to 'arch/x86/kernel')
-rw-r--r--arch/x86/kernel/cpu/perf_event.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 4ee3abf20ed6..cfa62ec090ec 100644
--- 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;

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