[PATCH net v2] mctp: accept MSG_CMSG_COMPAT in recvmsg

[PATCH net v2] mctp: accept MSG_CMSG_COMPAT in recvmsg

[Davidlohr Bueso]

32-bit userspace running on a 64-bit kernel is unable to receive MCTP
messages on an AF_MCTP socket, even though sending succeeds. There is
nothing for MCTP to do with it beyond not rejecting it, as af_packet,
af_key and can/isotp already do, for example.

Fixes: 833ef3b91de6 ("mctp: Populate socket implementation")
Cc: stable@vger.kernel.org
Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
---
Found while testing 32bit support for libcxlmi
Changes since v1:
  - target net and Cc stable
  - fix the corrupted hunk header

 net/mctp/af_mctp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/mctp/af_mctp.c b/net/mctp/af_mctp.c
index 8af5e2b3c8d1..aa22c0860712 100644
--- a/net/mctp/af_mctp.c
+++ b/net/mctp/af_mctp.c
@@ -292,7 +292,7 @@ static int mctp_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 	u8 type;
 	int rc;
 
-	if (flags & ~(MSG_DONTWAIT | MSG_TRUNC | MSG_PEEK))
+	if (flags & ~(MSG_DONTWAIT | MSG_TRUNC | MSG_PEEK | MSG_CMSG_COMPAT))
 		return -EOPNOTSUPP;
 
 	skb = skb_recv_datagram(sk, flags, &rc);
-- 
2.39.5

Re: [PATCH net v2] mctp: accept MSG_CMSG_COMPAT in recvmsg

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Thu,  5 Nov 2026 08:07:04 -0800 you wrote:
> 32-bit userspace running on a 64-bit kernel is unable to receive MCTP
> messages on an AF_MCTP socket, even though sending succeeds. There is
> nothing for MCTP to do with it beyond not rejecting it, as af_packet,
> af_key and can/isotp already do, for example.
> 
> Fixes: 833ef3b91de6 ("mctp: Populate socket implementation")
> Cc: stable@vger.kernel.org
> Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
> 
> [...]

Here is the summary with links:
  - [net,v2] mctp: accept MSG_CMSG_COMPAT in recvmsg
    https://git.kernel.org/netdev/net/c/350e1d0d3b38

You are awesome, thank you!
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