Re: [PATCH 1/2] net: socket: fix potential spectre v1 gadget in socketcall

[Josh Poimboeuf <jpoimboe@redhat.com>]

On Fri, Jul 27, 2018 at 10:43:01PM +0000, Jeremy Cline wrote:
> 'call' is a user-controlled value, so sanitize the array index after the
> bounds check to avoid speculating past the bounds of the 'nargs' array.
> 
> Found with the help of Smatch:
> 
> net/socket.c:2508 __do_sys_socketcall() warn: potential spectre issue
> 'nargs' [r] (local cap)
> 
> Cc: Josh Poimboeuf <jpoimboe@redhat.com>
> Cc: stable@vger.kernel.org
> Signed-off-by: Jeremy Cline <jcline@redhat.com>
> ---
>  net/socket.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/net/socket.c b/net/socket.c
> index 3015ddace71e..f15d5cbb3ba4 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -89,6 +89,7 @@
>  #include <linux/magic.h>
>  #include <linux/slab.h>
>  #include <linux/xattr.h>
> +#include <linux/nospec.h>
>  
>  #include <linux/uaccess.h>
>  #include <asm/unistd.h>
> @@ -2504,6 +2505,7 @@ SYSCALL_DEFINE2(socketcall, int, call, unsigned long __user *, args)
>  
>  	if (call < 1 || call > SYS_SENDMMSG)
>  		return -EINVAL;
> +	call = array_index_nospec(call, SYS_SENDMMSG + 1);
>  
>  	len = nargs[call];
>  	if (len > sizeof(a))

Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>

-- 
Josh