ipv4: avoid undefined behavior in do_ip_setsockopt()

(1<<optname) is undefined behavior in C with a negative optname or
optname larger than 31.  In those cases the result of the shift is
not necessarily zero (e.g., on x86).

This patch simplifies the code with a switch statement on optname.
It also allows the compiler to generate better code (e.g., using a
64-bit mask).

Signed-off-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 22 insertions, 13 deletions

diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index 5eea4a811042..14bbfcf717ac 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -457,19 +457,28 @@ static int do_ip_setsockopt(struct sock *sk, int level,
         struct inet_sock *inet = inet_sk(sk);
         int val = 0, err;
 
-        if (((1<<optname) & ((1<<IP_PKTINFO) | (1<<IP_RECVTTL) |
-                             (1<<IP_RECVOPTS) | (1<<IP_RECVTOS) |
-                             (1<<IP_RETOPTS) | (1<<IP_TOS) |
-                             (1<<IP_TTL) | (1<<IP_HDRINCL) |
-                             (1<<IP_MTU_DISCOVER) | (1<<IP_RECVERR) |
-                             (1<<IP_ROUTER_ALERT) | (1<<IP_FREEBIND) |
-                             (1<<IP_PASSSEC) | (1<<IP_TRANSPARENT) |
-                             (1<<IP_MINTTL) | (1<<IP_NODEFRAG))) ||
-            optname == IP_UNICAST_IF ||
-            optname == IP_MULTICAST_TTL ||
-            optname == IP_MULTICAST_ALL ||
-            optname == IP_MULTICAST_LOOP ||
-            optname == IP_RECVORIGDSTADDR) {
+        switch (optname) {
+        case IP_PKTINFO:
+        case IP_RECVTTL:
+        case IP_RECVOPTS:
+        case IP_RECVTOS:
+        case IP_RETOPTS:
+        case IP_TOS:
+        case IP_TTL:
+        case IP_HDRINCL:
+        case IP_MTU_DISCOVER:
+        case IP_RECVERR:
+        case IP_ROUTER_ALERT:
+        case IP_FREEBIND:
+        case IP_PASSSEC:
+        case IP_TRANSPARENT:
+        case IP_MINTTL:
+        case IP_NODEFRAG:
+        case IP_UNICAST_IF:
+        case IP_MULTICAST_TTL:
+        case IP_MULTICAST_ALL:
+        case IP_MULTICAST_LOOP:
+        case IP_RECVORIGDSTADDR:
                 if (optlen >= sizeof(int)) {
                         if (get_user(val, (int __user *) optval))
                                 return -EFAULT;