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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
(cherry picked from commit d29f1f53e5299e0bbb3e33ef8d35ed657fa633b6)

Signed-off-by: Willy Tarreau <w@1wt.eu>

diff --git a/net/socket.c b/net/socket.c
index 19671d8e20f682781492c74950e3fd2d7f1a53f4..a838a67dd77d4df595318a938965edc4582fa779 100644 (file)
--- a/net/socket.c
+++ b/net/socket.c
@@ -1872,6 +1872,9 @@ 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;