[PATCH] net: recvmmsg: Strip MSG_WAITFORONE when calling recvmsg

[PATCH] net: recvmmsg: Strip MSG_WAITFORONE when calling recvmsg

[Anton Blanchard]

recvmmsg fails on a raw socket with EINVAL. The reason for this is
packet_recvmsg checks the incoming flags:

        err = -EINVAL;
        if (flags & ~(MSG_PEEK|MSG_DONTWAIT|MSG_TRUNC|MSG_CMSG_COMPAT|MSG_ERRQUEUE))
                goto out;

This patch strips out MSG_WAITFORONE when calling recvmmsg which
fixes the issue.

Signed-off-by: Anton Blanchard <anton@samba.org>
Cc: stable@kernel.org [2.6.34+]
---

We could also add MSG_WAITFORONE to the raw socket recvmsg check, or
just remove the check completely. Thoughts?

Index: linux-net/net/socket.c
===================================================================
--- linux-net.orig/net/socket.c	2011-05-09 08:59:22.757767314 +1000
+++ linux-net/net/socket.c	2011-05-16 17:14:52.501268819 +1000
@@ -2232,14 +2232,16 @@ int __sys_recvmmsg(int fd, struct mmsghd
 		 */
 		if (MSG_CMSG_COMPAT & flags) {
 			err = __sys_recvmsg(sock, (struct msghdr __user *)compat_entry,
-					    &msg_sys, flags, datagrams);
+					    &msg_sys, flags & ~MSG_WAITFORONE,
+					    datagrams);
 			if (err < 0)
 				break;
 			err = __put_user(err, &compat_entry->msg_len);
 			++compat_entry;
 		} else {
 			err = __sys_recvmsg(sock, (struct msghdr __user *)entry,
-					    &msg_sys, flags, datagrams);
+					    &msg_sys, flags & ~MSG_WAITFORONE,
+					    datagrams);
 			if (err < 0)
 				break;
 			err = put_user(err, &entry->msg_len);

Re: [PATCH] net: recvmmsg: Strip MSG_WAITFORONE when calling recvmsg

[David Miller]

From: Anton Blanchard <anton@samba.org>
Date: Tue, 17 May 2011 08:59:24 +1000

> 
> recvmmsg fails on a raw socket with EINVAL. The reason for this is
> packet_recvmsg checks the incoming flags:
> 
>         err = -EINVAL;
>         if (flags & ~(MSG_PEEK|MSG_DONTWAIT|MSG_TRUNC|MSG_CMSG_COMPAT|MSG_ERRQUEUE))
>                 goto out;
> 
> This patch strips out MSG_WAITFORONE when calling recvmmsg which
> fixes the issue.
> 
> Signed-off-by: Anton Blanchard <anton@samba.org>
> Cc: stable@kernel.org [2.6.34+]
> ---
> 
> We could also add MSG_WAITFORONE to the raw socket recvmsg check, or
> just remove the check completely. Thoughts?

I think both should be done.

Tests like the one packet_recvmsg() is doing makes it really hard to
add new MSG_* flags generically (ie. by adding the flag and having
some generic socket operation all recvmsg() implementations call
process that flag bit in some way).

It should just explicitly check for the bits it doesn't support.

And recvmmsg() should clear the bit because it is a completely
internal thing.  It's similar to how we hide MSG_CMSG_COMPAT from
userspace.

Anyways I'll apply this patch, and feel free to submit the other
one.

Thanks.