[PATCH] ipc: shm: fix information leak to userland

[Vasiliy Kulikov <segooon@gmail.com>]

Structure shmid_ds is copied to userland with shm_unused{,2,3}
fields unitialized.  It leads to leaking of contents of kernel stack
memory.

Cc: stable@kernel.org
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Vasiliy Kulikov <segooon@gmail.com>
---
 Compile tested.

 ipc/shm.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/ipc/shm.c b/ipc/shm.c
index fd658a1..7d3bb22 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -479,6 +479,7 @@ static inline unsigned long copy_shmid_to_user(void __user *buf, struct shmid64_
 	    {
 		struct shmid_ds out;
 
+		memset(&out, 0, sizeof(out));
 		ipc64_perm_to_ipc_perm(&in->shm_perm, &out.shm_perm);
 		out.shm_segsz	= in->shm_segsz;
 		out.shm_atime	= in->shm_atime;
-- 
1.7.0.4