ipv4: do compat setsockopt for MCAST_MSFILTER directly

Parallel to what the native setsockopt() does, except that unlike
the native setsockopt() we do not use memdup_user() - we want
the sockaddr_storage fields properly aligned, so we allocate
4 bytes more and copy compat_group_filter at the offset 4,
which yields the proper alignments.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index cc04411..b6b889b 100644 (file)
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -1286,9 +1286,55 @@ int compat_ip_setsockopt(struct sock *sk, int level, int optname,
        case MCAST_LEAVE_SOURCE_GROUP:
        case MCAST_BLOCK_SOURCE:
        case MCAST_UNBLOCK_SOURCE:
-       case MCAST_MSFILTER:
                return compat_mc_setsockopt(sk, level, optname, optval, optlen,
                        ip_setsockopt);
+       case MCAST_MSFILTER:
+       {
+               const int size0 = offsetof(struct compat_group_filter, gf_slist);
+               struct compat_group_filter *gf32;
+               void *p;
+               int n;
+
+               if (optlen < size0)
+                       return -EINVAL;
+               if (optlen > sysctl_optmem_max - 4)
+                       return -ENOBUFS;
+
+               p = kmalloc(optlen + 4, GFP_KERNEL);
+               if (!p)
+                       return -ENOMEM;
+               gf32 = p + 4; /* we want ->gf_group and ->gf_slist aligned */
+               if (copy_from_user(gf32, optval, optlen)) {
+                       err = -EFAULT;
+                       goto mc_msf_out;
+               }
+
+               n = gf32->gf_numsrc;
+               /* numsrc >= (4G-140)/128 overflow in 32 bits */
+               if (n >= 0x1ffffff) {
+                       err = -ENOBUFS;
+                       goto mc_msf_out;
+               }
+               if (offsetof(struct compat_group_filter, gf_slist[n]) > optlen) {
+                       err = -EINVAL;
+                       goto mc_msf_out;
+               }
+
+               rtnl_lock();
+               lock_sock(sk);
+               /* numsrc >= (4G-140)/128 overflow in 32 bits */
+               if (n > sock_net(sk)->ipv4.sysctl_igmp_max_msf)
+                       err = -ENOBUFS;
+               else
+                       err = set_mcast_msfilter(sk, gf32->gf_interface,
+                                                n, gf32->gf_fmode,
+                                                &gf32->gf_group, gf32->gf_slist);
+               release_sock(sk);
+               rtnl_unlock();
+mc_msf_out:
+               kfree(p);
+               return err;
+       }
        }
 
        err = do_ip_setsockopt(sk, level, optname, optval, optlen);