From: Andrey Vagin <avagin@openvz.org>
To: linux-kernel@vger.kernel.org
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
Paul Mackerras <paulus@samba.org>, Ingo Molnar <mingo@elte.hu>,
Arnaldo Carvalho de Melo <acme@ghostprotocols.net>,
avagin@openvz.org
Subject: [PATCH] x86, perf: check that current->mm alive before getting user callchain
Date: Tue, 30 Aug 2011 12:32:36 +0400 [thread overview]
Message-ID: <1314693156-24131-1-git-send-email-avagin@openvz.org> (raw)
An event may occurs when mm is already released.
I added an event in dequeue_entity and caught panic with 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>
---
arch/x86/kernel/cpu/perf_event.c | 3 +++
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 4ee3abf..cfa62ec 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;
--
1.7.3.4
next reply other threads:[~2011-08-30 8:33 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-30 8:32 Andrey Vagin [this message]
2011-08-30 13:14 ` Peter Zijlstra
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1314693156-24131-1-git-send-email-avagin@openvz.org \
--to=avagin@openvz.org \
--cc=a.p.zijlstra@chello.nl \
--cc=acme@ghostprotocols.net \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@elte.hu \
--cc=paulus@samba.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®