linux-kernel - [tip:perf/urgent] perf: Fix alloc_callchain

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Message-ID: <tip-10f633a1a5cd8b9e2605d1f64a14ca008bce962b@git.kernel.org>
Date:	Wed, 26 Jan 2011 07:25:37 GMT
From:	tip-bot for Eric Dumazet <eric.dumazet@...il.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, eranian@...gle.com, acme@...hat.com,
	hpa@...or.com, mingo@...hat.com, eric.dumazet@...il.com,
	a.p.zijlstra@...llo.nl, davem@...emloft.net, fweisbec@...il.com,
	tglx@...utronix.de, mingo@...e.hu
Subject: [tip:perf/urgent] perf: Fix alloc_callchain_buffers()

Commit-ID:  10f633a1a5cd8b9e2605d1f64a14ca008bce962b
Gitweb:     http://git.kernel.org/tip/10f633a1a5cd8b9e2605d1f64a14ca008bce962b
Author:     Eric Dumazet <eric.dumazet@...il.com>
AuthorDate: Tue, 25 Jan 2011 19:40:51 +0100
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Wed, 26 Jan 2011 07:55:15 +0100

perf: Fix alloc_callchain_buffers()

Commit 927c7a9e92c4 ("perf: Fix race in callchains") introduced
a mismatch in the sizing of struct callchain_cpus_entries.

nr_cpu_ids must be used instead of num_possible_cpus(), or we
might get out of bound memory accesses on some machines.

Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: David Miller <davem@...emloft.net>
Cc: Stephane Eranian <eranian@...gle.com>
CC: stable@...nel.org
LKML-Reference: <1295980851.3588.351.camel@...mazet-laptop>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 kernel/perf_event.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 126a302..852ae8c 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -1999,8 +1999,7 @@ static int alloc_callchain_buffers(void)
 	 * accessed from NMI. Use a temporary manual per cpu allocation
 	 * until that gets sorted out.
 	 */
-	size = sizeof(*entries) + sizeof(struct perf_callchain_entry *) *
-		num_possible_cpus();
+	size = offsetof(struct callchain_cpus_entries, cpu_entries[nr_cpu_ids]);
 
 	entries = kzalloc(size, GFP_KERNEL);
 	if (!entries)
--
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