From: Marco Elver <elver@google.com>
To: elver@google.com, peterz@infradead.org, mingo@redhat.com,
acme@kernel.org, mark.rutland@arm.com,
alexander.shishkin@linux.intel.com, jolsa@redhat.com,
namhyung@kernel.org, linux-perf-users@vger.kernel.org,
linux-kernel@vger.kernel.org
Cc: kasan-dev@googlegroups.com, dvyukov@google.com,
syzbot+142c9018f5962db69c7e@syzkaller.appspotmail.com
Subject: [PATCH] perf: Fix data race between pin_count increment/decrement
Date: Thu, 27 May 2021 12:47:11 +0200 [thread overview]
Message-ID: <20210527104711.2671610-1-elver@google.com> (raw)
KCSAN reports a data race between increment and decrement of pin_count:
write to 0xffff888237c2d4e0 of 4 bytes by task 15740 on cpu 1:
find_get_context kernel/events/core.c:4617
__do_sys_perf_event_open kernel/events/core.c:12097 [inline]
__se_sys_perf_event_open kernel/events/core.c:11933
...
read to 0xffff888237c2d4e0 of 4 bytes by task 15743 on cpu 0:
perf_unpin_context kernel/events/core.c:1525 [inline]
__do_sys_perf_event_open kernel/events/core.c:12328 [inline]
__se_sys_perf_event_open kernel/events/core.c:11933
...
Because neither read-modify-write here is atomic, this can lead to one of the
operations being lost, resulting in an inconsistent pin_count. Fix it by adding
the missing locking in the CPU-event case.
Reported-by: syzbot+142c9018f5962db69c7e@syzkaller.appspotmail.com
Signed-off-by: Marco Elver <elver@google.com>
---
kernel/events/core.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 6fee4a7e88d7..fe88d6eea3c2 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4609,7 +4609,9 @@ find_get_context(struct pmu *pmu, struct task_struct *task,
cpuctx = per_cpu_ptr(pmu->pmu_cpu_context, cpu);
ctx = &cpuctx->ctx;
get_ctx(ctx);
+ raw_spin_lock_irqsave(&ctx->lock, flags);
++ctx->pin_count;
+ raw_spin_unlock_irqrestore(&ctx->lock, flags);
return ctx;
}
--
2.31.1.818.g46aad6cb9e-goog
next reply other threads:[~2021-05-27 10:47 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-27 10:47 Marco Elver [this message]
2021-05-27 10:57 ` [PATCH] perf: Fix data race between pin_count increment/decrement Peter Zijlstra
2021-05-31 10:40 ` [tip: perf/urgent] " tip-bot2 for Marco Elver
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=20210527104711.2671610-1-elver@google.com \
--to=elver@google.com \
--cc=acme@kernel.org \
--cc=alexander.shishkin@linux.intel.com \
--cc=dvyukov@google.com \
--cc=jolsa@redhat.com \
--cc=kasan-dev@googlegroups.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-perf-users@vger.kernel.org \
--cc=mark.rutland@arm.com \
--cc=mingo@redhat.com \
--cc=namhyung@kernel.org \
--cc=peterz@infradead.org \
--cc=syzbot+142c9018f5962db69c7e@syzkaller.appspotmail.com \
/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;
as well as URLs for NNTP newsgroup(s).