net:socket: set msg_namelen to 0 if msg_name is passed as NULL in msghdr struct from...

commit 6a2a2b3ae0759843b22c929881cc184b00cc63ff upstream.

Linux manpage for recvmsg and sendmsg calls does not explicitly mention setting msg_namelen to 0 when
msg_name passed set as NULL. When developers don't set msg_namelen member in msghdr, it might contain garbage
value which will fail the validation check and sendmsg and recvmsg calls from kernel will return EINVAL. This will
break old binaries and any code for which there is no access to source code.
To fix this, we set msg_namelen to 0 when msg_name is passed as NULL from userland.

Signed-off-by: Ani Sinha <ani@arista.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Cc: Michal Marek <mmarek@suse.cz>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

diff --git a/net/socket.c b/net/socket.c
index 7050240a951b55ff5e73b4bb7b55c17250942fcd..4980af97d87c754db26df321abdf124762b8d6c0 100644 (file)
--- a/net/socket.c
+++ b/net/socket.c
@@ -1985,6 +1985,9 @@ static int copy_msghdr_from_user(struct msghdr *kmsg,
        if (copy_from_user(kmsg, umsg, sizeof(struct msghdr)))
                return -EFAULT;
 
+       if (kmsg->msg_name == NULL)
+               kmsg->msg_namelen = 0;
+
        if (kmsg->msg_namelen < 0)
                return -EINVAL;