[PATCH v2] ipc: initialize structure memory to zero for shmctl

[PATCH v2] ipc: initialize structure memory to zero for shmctl

[Kees Cook]

The old shm interface will leak a few bytes of stack contents. Explicitly
initialize the structure to zero-fill the untouched fields, using memset
instead of C99-style in case there are ever holes in the structure.

Signed-off-by: Kees Cook <kees.cook@canonical.com>
---
 ipc/shm.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/ipc/shm.c b/ipc/shm.c
index 52ed77e..f943b1e 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -473,6 +473,7 @@ 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;
@@ -524,6 +525,7 @@ static inline unsigned long copy_shminfo_to_user(void __user *buf, struct shminf
 	    {
 		struct shminfo out;
 
+		memset(&out, 0, sizeof(out));
 		if(in->shmmax > INT_MAX)
 			out.shmmax = INT_MAX;
 		else
-- 
1.7.1


-- 
Kees Cook
Ubuntu Security Team

Re: [stable] [PATCH v2] ipc: initialize structure memory to zero for shmctl

[Greg KH]

On Wed, Oct 06, 2010 at 07:18:36PM -0700, Kees Cook wrote:
> The old shm interface will leak a few bytes of stack contents. Explicitly
> initialize the structure to zero-fill the untouched fields, using memset
> instead of C99-style in case there are ever holes in the structure.
> 
> Signed-off-by: Kees Cook <kees.cook@canonical.com>
> ---

If you wish to have a patch included in the stable series, please read
Documentation/stable_kernel_rules.txt which state that adding a:
	Cc: stable <stable@kernel.org>
to the signed-off-by: area will cause it to be automagically included
when the patch gets into Linus's tree.  Otherwise it just causes a lot
of extra work for me to dig around and watch out for it in the future.

thanks,

greg k-h