linux-kernel - [150/151] perf_event: Fix incorrect range check on cpu number

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Date:	Wed, 16 Dec 2009 19:57:27 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: [150/151] perf_event: Fix incorrect range check on cpu number

2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Paul Mackerras <paulus@...ba.org>

commit 0f624e7e5625f4c30c836b7a5decfe2553582391 upstream.

It is quite legitimate for CPUs to be numbered sparsely, meaning
that it possible for an online CPU to have a number which is
greater than the total count of possible CPUs.

Currently find_get_context() has a sanity check on the cpu
number where it checks it against num_possible_cpus().  This
test can fail for a legitimate cpu number if the
cpu_possible_mask is sparsely populated.

This fixes the problem by checking the CPU number against
nr_cpumask_bits instead, since that is the appropriate check to
ensure that the cpu number is same to pass to cpu_isset()
subsequently.

Reported-by: Michael Neuling <mikey@...ling.org>
Signed-off-by: Paul Mackerras <paulus@...ba.org>
Tested-by: Michael Neuling <mikey@...ling.org>
Acked-by: Peter Zijlstra <peterz@...radead.org>
LKML-Reference: <20091215084032.GA18661@...ck.ozlabs.ibm.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 kernel/perf_event.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -1583,7 +1583,7 @@ static struct perf_event_context *find_g
 		if (perf_paranoid_cpu() && !capable(CAP_SYS_ADMIN))
 			return ERR_PTR(-EACCES);
 
-		if (cpu < 0 || cpu > num_possible_cpus())
+		if (cpu < 0 || cpu >= nr_cpumask_bits)
 			return ERR_PTR(-EINVAL);
 
 		/*


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