Re: [PATCH 3.14 30/44] signalfd: fix information leak in signalfd_copyinfo

[Luis Henriques]

On Fri, Aug 14, 2015 at 10:45:07AM -0700, Greg Kroah-Hartman wrote:
> 3.14-stable review patch.  If anyone has any objections, please let me know.
>

These 3 patches seem to be relevant to other stable trees as well.  I'm
queuing them for the 3.16 kernel.

Cheers,
--
Luís


> ------------------
> 
> From: Amanieu d'Antras <amanieu@xxxxxxxxx>
> 
> commit 3ead7c52bdb0ab44f4bb1feed505a8323cc12ba7 upstream.
> 
> This function may copy the si_addr_lsb field to user mode when it hasn't
> been initialized, which can leak kernel stack data to user mode.
> 
> Just checking the value of si_code is insufficient because the same
> si_code value is shared between multiple signals.  This is solved by
> checking the value of si_signo in addition to si_code.
> 
> Signed-off-by: Amanieu d'Antras <amanieu@xxxxxxxxx>
> Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> 
> ---
>  fs/signalfd.c |    5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> --- a/fs/signalfd.c
> +++ b/fs/signalfd.c
> @@ -121,8 +121,9 @@ static int signalfd_copyinfo(struct sign
>  		 * Other callers might not initialize the si_lsb field,
>  		 * so check explicitly for the right codes here.
>  		 */
> -		if (kinfo->si_code == BUS_MCEERR_AR ||
> -		    kinfo->si_code == BUS_MCEERR_AO)
> +		if (kinfo->si_signo == SIGBUS &&
> +		    (kinfo->si_code == BUS_MCEERR_AR ||
> +		     kinfo->si_code == BUS_MCEERR_AO))
>  			err |= __put_user((short) kinfo->si_addr_lsb,
>  					  &uinfo->ssi_addr_lsb);
>  #endif
> 
> 
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