Ack: [Precise][SRU] Yama: handle 32-bit userspace prctl

[Brad Figg]

On 07/07/2014 10:49 PM, Kees Cook wrote:
> BugLink: http://bugs.launchpad.net/bugs/1338883
> 
> commit 2e4930eb7c8fb20a39dfb5f8a8f80402710dcea8 upstream.
> 
> When running a 64-bit kernel and receiving prctls from a 32-bit
> userspace, the "-1" used as an unsigned long will end up being
> misdetected. The kernel is looking for 0xffffffffffffffff instead of
> 0xffffffff. Since prctl lacks a distinct compat interface, Yama needs
> to handle this translation itself. As such, support either value as
> meaning PR_SET_PTRACER_ANY, to avoid breaking the ABI for 64-bit.
> 
> Signed-off-by: Kees Cook <keescook at chromium.org>
> Acked-by: John Johansen <john.johansen at canonical.com>
> Cc: stable at vger.kernel.org
> Signed-off-by: James Morris <james.l.morris at oracle.com>
> 
> [adjusted for Precise's Yama backport format/whitespace changes]
> Signed-off-by: Kees Cook <kees at ubuntu.com>
> ---
>  security/yama/yama_lsm.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
> index 30361cb..84bd07b 100644
> --- a/security/yama/yama_lsm.c
> +++ b/security/yama/yama_lsm.c
> @@ -140,8 +140,7 @@ int yama_task_prctl(int option, unsigned long arg2, unsigned long arg3,
>  		if (arg2 == 0) {
>  			yama_ptracer_del(NULL, myself);
>  			rc = 0;
> -		}
> -		else if (arg2 == PR_SET_PTRACER_ANY) {
> +		} else if (arg2 == PR_SET_PTRACER_ANY || (int)arg2 == -1) {
>  			rc = yama_ptracer_add(NULL, myself);
>  		} else {
>  			struct task_struct *tracer;
>