[PATCH 4.4 120/124] net: socket: fix potential spectre v1 gadget in socketcall

From: Greg Kroah-Hartman
Date: Sat Aug 04 2018 - 05:12:28 EST


4.4-stable review patch. If anyone has any objections, please let me know.

------------------

From: Jeremy Cline <jcline@xxxxxxxxxx>

commit c8e8cd579bb4265651df8223730105341e61a2d1 upstream.

'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@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Jeremy Cline <jcline@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
net/socket.c | 2 ++
1 file changed, 2 insertions(+)

--- 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 <asm/uaccess.h>
#include <asm/unistd.h>
@@ -2324,6 +2325,7 @@ SYSCALL_DEFINE2(socketcall, int, call, u

if (call < 1 || call > SYS_SENDMMSG)
return -EINVAL;
+ call = array_index_nospec(call, SYS_SENDMMSG + 1);

len = nargs[call];
if (len > sizeof(a))