From: Peter Zijlstra <peterz@infradead.org>
Date: Thu, 2 Oct 2014 23:17:02 +0000 (-0700)
Subject: perf: fix perf bug in fork()
X-Git-Tag: fixes-for-v3.18-merge-window~48^2~1
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6c72e3501d0d62fc064d3680e5234f3463ec5a86;p=pandora-kernel.git

perf: fix perf bug in fork()

Oleg noticed that a cleanup by Sylvain actually uncovered a bug; by
calling perf_event_free_task() when failing sched_fork() we will not yet
have done the memset() on ->perf_event_ctxp[] and will therefore try and
'free' the inherited contexts, which are still in use by the parent
process.  This is bad..

Suggested-by: Oleg Nesterov <oleg@redhat.com>
Reported-by: Oleg Nesterov <oleg@redhat.com>
Reported-by: Sylvain 'ythier' Hitier <sylvain.hitier@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/kernel/events/core.c b/kernel/events/core.c
index d640a8b4dcbc..963bf139e2b2 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7948,8 +7948,10 @@ int perf_event_init_task(struct task_struct *child)
 
 	for_each_task_context_nr(ctxn) {
 		ret = perf_event_init_context(child, ctxn);
-		if (ret)
+		if (ret) {
+			perf_event_free_task(child);
 			return ret;
+		}
 	}
 
 	return 0;
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