[patch 15/45] perf_counter: Fix buffer overflow in perf_copy_attr()

[Greg KH]

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

------------------
From: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxx>

commit b3e62e35058fc744ac794611f4e79bcd1c5a4b83 upstream.

If we pass a big size data over perf_counter_open() syscall,
the kernel will copy this data to a small buffer, it will
cause kernel crash.

This bug makes the kernel unsafe and non-root local user can
trigger it.

Signed-off-by: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxx>
Acked-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Acked-by: Paul Mackerras <paulus@xxxxxxxxx>
LKML-Reference: <4AAF37D4.5010706@xxxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 kernel/perf_counter.c |    1 +
 1 file changed, 1 insertion(+)

--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -4171,6 +4171,7 @@ static int perf_copy_attr(struct perf_co
 			if (val)
 				goto err_size;
 		}
+		size = sizeof(*attr);
 	}
 
 	ret = copy_from_user(attr, uattr, size);


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