[PATCH net 1/2] net: check the sendmsg LSM hook for every batched message

[PATCH net 1/2] net: check the sendmsg LSM hook for every batched message

[Avi Weiss]

sendmmsg() skips security_socket_sendmsg() when two consecutive
messages have the same explicit destination address. The comparison
does not account for the message size, so a BPF LSM policy that denies
large sends can be bypassed by placing an allowed message first.

Use __sock_sendmsg() for the cached-destination case as well, so that
every message undergoes the LSM check. Keep the remainder of the
address-caching logic unchanged in this minimal correction.

Fixes: 228e548e6020 ("net: Add sendmmsg socket system call")
Signed-off-by: Avi Weiss <thnkslprpt@gmail.com>
---
 net/socket.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/socket.c b/net/socket.c
index 2e3b5737c481..c2a85224ab55 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -2709,7 +2709,7 @@ static int ____sys_sendmsg(struct socket *sock, struct msghdr *msg_sys,
 	    used_address->name_len == msg_sys->msg_namelen &&
 	    !memcmp(&used_address->name, msg_sys->msg_name,
 		    used_address->name_len)) {
-		err = sock_sendmsg_nosec(sock, msg_sys);
+		err = __sock_sendmsg(sock, msg_sys);
 		goto out_freectl;
 	}
 	err = __sock_sendmsg(sock, msg_sys);
-- 
2.43.0

Re: [PATCH net 1/2] net: check the sendmsg LSM hook for every batched message

[netdev-bot+sinfo]

Hi!

This is an automated message. This series looks like a fix, but its
commit messages seem to be missing some information:

 - How the issue was discovered, e.g. hit in production, hit during
   development, syzbot report, manual code inspection, LLM or static
   analysis tool scan.

 - Whether the issue was actually triggered, or is only theoretical
   (e.g. found by code inspection). If it was triggered please include
   the symptoms, like the stack trace or error messages.

Please do not repost the series just to address the above. Instead,
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