[PATCH] perf_counter: fix buffer overflow in perf_copy_attr()

[Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>]

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 make kernel unsafe and no-root user can trigger it.

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
 kernel/perf_counter.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 667ab25..75c46c0 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -4216,6 +4216,7 @@ static int perf_copy_attr(struct perf_counter_attr __user *uattr,
 			if (val)
 				goto err_size;
 		}
+		size = sizeof(*attr);
 	}
 
 	ret = copy_from_user(attr, uattr, size);
-- 
1.6.1.2