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