ax25: avoid overflows in ax25_setsockopt()

Commit be639ac6 ("NET: AX.25: Check ioctl arguments to avoid overflows
further down the road") rejects very large arguments, but doesn't
completely fix overflows on 64-bit systems.  Consider the AX25_T2 case.

	int opt;
	...
	if (opt < 1 || opt > ULONG_MAX / HZ) {
		res = -EINVAL;
		break;
	}
	ax25->t2 = opt * HZ;

The 32-bit multiplication opt * HZ would overflow before being assigned
to 64-bit ax25->t2.  This patch changes "opt" to unsigned long.

Signed-off-by: Xi Wang <xi.wang@gmail.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 5 deletions

diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c
index b863c1877c80..3cd0a0dc91cb 100644
--- a/net/ax25/af_ax25.c
+++ b/net/ax25/af_ax25.c
@@ -545,15 +545,16 @@ static int ax25_setsockopt(struct socket *sock, int level, int optname,
         ax25_cb *ax25;
         struct net_device *dev;
         char devname[IFNAMSIZ];
-        int opt, res = 0;
+        unsigned long opt;
+        int res = 0;
 
         if (level != SOL_AX25)
                 return -ENOPROTOOPT;
 
-        if (optlen < sizeof(int))
+        if (optlen < sizeof(unsigned int))
                 return -EINVAL;
 
-        if (get_user(opt, (int __user *)optval))
+        if (get_user(opt, (unsigned int __user *)optval))
                 return -EFAULT;
 
         lock_sock(sk);
@@ -609,7 +610,7 @@ static int ax25_setsockopt(struct socket *sock, int level, int optname,
                 break;
 
         case AX25_IDLE:
-                if (opt < 0 || opt > ULONG_MAX / (60 * HZ)) {
+                if (opt > ULONG_MAX / (60 * HZ)) {
                         res = -EINVAL;
                         break;
                 }
@@ -617,7 +618,7 @@ static int ax25_setsockopt(struct socket *sock, int level, int optname,
                 break;
 
         case AX25_BACKOFF:
-                if (opt < 0 || opt > 2) {
+                if (opt > 2) {
                         res = -EINVAL;
                         break;
                 }