ipc: shm: fix information leak to userland

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

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

1 files changed, 1 insertions, 0 deletions

diff --git a/ipc/shm.c b/ipc/shm.c
index fd658a1c2b88..7d3bb22a9302 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;