[tip:perf/urgent] perf: Fix alloc_callchain_buffers()

From: tip-bot for Eric Dumazet
Date: Thu Jan 27 2011 - 13:28:40 EST

Commit-ID: 88d4f0db7fa8785859c1d637f9aac210932b6216
Gitweb: http://git.kernel.org/tip/88d4f0db7fa8785859c1d637f9aac210932b6216
Author: Eric Dumazet <eric.dumazet@xxxxxxxxx>
AuthorDate: Tue, 25 Jan 2011 19:40:51 +0100
Committer: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Thu, 27 Jan 2011 19:21:50 +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@xxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: David Miller <davem@xxxxxxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
CC: stable@xxxxxxxxxx
LKML-Reference: <1295980851.3588.351.camel@edumazet-laptop>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
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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