ipv4: avoid undefined behavior in do_ip_setsockopt()

[ Upstream commit 0c9f79be295c99ac7e4b569ca493d75fdcc19e4e ]

(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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index 09ff51b..0106d25 100644 (file)
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -468,18 +468,27 @@ 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_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_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;