perf: Fix alloc_callchain_buffers()

Commit 927c7a9 ("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 <[email protected]> Cc: Frederic Weisbecker <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Arnaldo Carvalho de Melo <[email protected]> Cc: David Miller <[email protected]> Cc: Stephane Eranian <[email protected]> CC: [email protected] LKML-Reference: <1295980851.3588.351.camel@edumazet-laptop> Signed-off-by: Ingo Molnar <[email protected]>
chewitt · Jan 27, 2011 · 88d4f0d · 88d4f0d
1 parent 6fb1b30
commit 88d4f0d
Showing 1 changed file with 1 addition and 2 deletions.
diff --git 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)