From Quentin Casasnovas <> Subject [PATCH] RDS: fix race condition when sending a message on unbound socket. Date Fri, 16 Oct 2015 17:11:42 +0200 Sasha's found a NULL pointer dereference in the RDS connection code when sending a message to an apparently unbound socket. The problem is caused by the code checking if the socket is bound in rds_sendmsg(), which checks the rs_bound_addr field without taking a lock on the socket. This opens a race where rs_bound_addr is temporarily set but where the transport is not in rds_bind(), leading to a NULL pointer dereference when trying to dereference 'trans' in __rds_conn_create(). Vegard wrote a reproducer for this issue, so kindly ask him to share if you're interested. I cannot reproduce the NULL pointer dereference using Vegard's reproducer with this patch, whereas I could without. Complete earlier incomplete fix to CVE-2015-6937: 74e98eb08588 ("RDS: verify the underlying transport exists before creating a connection") Signed-off-by: Quentin Casasnovas Reviewed-by: Vegard Nossum Reviewed-by: Sasha Levin Cc: Vegard Nossum Cc: Sasha Levin Cc: Chien Yen Cc: Santosh Shilimkar Cc: David S. Miller Cc: stable@vger.kernel.org --- diff -ru a/net/rds/send.c b/net/rds/send.c --- a/net/rds/send.c 2015-08-30 11:34:09.000000000 -0700 +++ b/net/rds/send.c 2016-02-03 15:10:09.535283384 -0800 @@ -986,11 +986,13 @@ release_sock(sk); } - /* racing with another thread binding seems ok here */ + lock_sock(sk); if (daddr == 0 || rs->rs_bound_addr == 0) { + release_sock(sk); ret = -ENOTCONN; /* XXX not a great errno */ goto out; } + release_sock(sk); /* size of rm including all sgs */ ret = rds_rm_size(msg, payload_len); -- 2.4.9