get rid of compat_mc_getsockopt()

now we can do MCAST_MSFILTER in compat ->getsockopt() without
playing silly buggers with copying things back and forth.
We can form a native struct group_filter (sans the variable-length
tail) on stack, pass that + pointer to the tail of original request
to the helper doing the bulk of the work, then do the rest of
copyout - same as the native getsockopt() does.

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

1 files changed, 41 insertions, 3 deletions

diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index e3703a3e7ef4..65a30e7672ff 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -1607,9 +1607,47 @@ int compat_ip_getsockopt(struct sock *sk, int level, int optname,
 {
 	int err;
 
-	if (optname == MCAST_MSFILTER)
-		return compat_mc_getsockopt(sk, level, optname, optval, optlen,
-			ip_getsockopt);
+	if (optname == MCAST_MSFILTER) {
+		const int size0 = offsetof(struct compat_group_filter, gf_slist);
+		struct compat_group_filter __user *p = (void __user *)optval;
+		struct compat_group_filter gf32;
+		struct group_filter gf;
+		int ulen, err;
+		int num;
+
+		if (level != SOL_IP)
+			return -EOPNOTSUPP;
+
+		if (get_user(ulen, optlen))
+			return -EFAULT;
+
+		if (ulen < size0)
+			return -EINVAL;
+
+		if (copy_from_user(&gf32, p, size0))
+			return -EFAULT;
+
+		gf.gf_interface = gf32.gf_interface;
+		gf.gf_fmode = gf32.gf_fmode;
+		num = gf.gf_numsrc = gf32.gf_numsrc;
+		gf.gf_group = gf32.gf_group;
+
+		rtnl_lock();
+		lock_sock(sk);
+		err = ip_mc_gsfget(sk, &gf, p->gf_slist);
+		release_sock(sk);
+		rtnl_unlock();
+		if (err)
+			return err;
+		if (gf.gf_numsrc < num)
+			num = gf.gf_numsrc;
+		ulen = GROUP_FILTER_SIZE(num) - (sizeof(gf) - sizeof(gf32));
+		if (put_user(ulen, optlen) ||
+		    put_user(gf.gf_fmode, &p->gf_fmode) ||
+		    put_user(gf.gf_numsrc, &p->gf_numsrc))
+			return -EFAULT;
+		return 0;
+	}
 
 	err = do_ip_getsockopt(sk, level, optname, optval, optlen,
 		MSG_CMSG_COMPAT);