[Dapper/Hardy/Karmic/Maverick] [CVE-2010-4083] [PATCH 1/1] sys_semctl: fix kernel stack leakage, CVE-2010-4083

[Stefan Bader]

On 02/04/2011 06:26 PM, Brad Figg wrote:
> From: Dan Rosenberg <drosenberg at vsecurity.com>
> 
> CVE-2010-4083
> 
> BugLink: http://bugs.launchpad.net/bugs/712749
> 
> The semctl syscall has several code paths that lead to the leakage of
> uninitialized kernel stack memory (namely the IPC_INFO, SEM_INFO,
> IPC_STAT, and SEM_STAT commands) during the use of the older, obsolete
> version of the semid_ds struct.
> 
> The copy_semid_to_user() function declares a semid_ds struct on the stack
> and copies it back to the user without initializing or zeroing the
> "sem_base", "sem_pending", "sem_pending_last", and "undo" pointers,
> allowing the leakage of 16 bytes of kernel stack memory.
> 
> The code is still reachable on 32-bit systems - when calling semctl()
> newer glibc's automatically OR the IPC command with the IPC_64 flag, but
> invoking the syscall directly allows users to use the older versions of
> the struct.
> 
> Signed-off-by: Dan Rosenberg <dan.j.rosenberg at gmail.com>
> Cc: Manfred Spraul <manfred at colorfullife.com>
> Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
> Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
> 
> (cherry-picked from commit 982f7c2b2e6a28f8f266e075d92e19c0dd4c6e56)
> Signed-off-by: Brad Figg <brad.figg at canonical.com>
Acked-by: Stefan Bader <stefan.bader at canonical.com>
> ---
>  ipc/sem.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/ipc/sem.c b/ipc/sem.c
> index 40a8f46..0e0d49b 100644
> --- a/ipc/sem.c
> +++ b/ipc/sem.c
> @@ -743,6 +743,8 @@ static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in,
>  	    {
>  		struct semid_ds out;
>  
> +		memset(&out, 0, sizeof(out));
> +
>  		ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
>  
>  		out.sem_otime	= in->sem_otime;