xsk: Fix memory leak for failed bind

stable inclusion
from stable-5.10.7
commit 0fae7d269ef7343e052bb66d4f79022e4456fe82
bugzilla: 47429

--------------------------------

commit 8bee6833 upstream.

Fix a possible memory leak when a bind of an AF_XDP socket fails. When
the fill and completion rings are created, they are tied to the
socket. But when the buffer pool is later created at bind time, the
ownership of these two rings are transferred to the buffer pool as
they might be shared between sockets (and the buffer pool cannot be
created until we know what we are binding to). So, before the buffer
pool is created, these two rings are cleaned up with the socket, and
after they have been transferred they are cleaned up together with
the buffer pool.

The problem is that ownership was transferred before it was absolutely
certain that the buffer pool could be created and initialized
correctly and when one of these errors occurred, the fill and
completion rings did neither belong to the socket nor the pool and
where therefore leaked. Solve this by moving the ownership transfer
to the point where the buffer pool has been completely set up and
there is no way it can fail.

Fixes: 7361f9c3 ("xsk: Move fill and completion rings to buffer pool")
Reported-by: syzbot+cfa88ddd0655afa88763@syzkaller.appspotmail.com
Signed-off-by: NMagnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>
Acked-by: NBjörn Töpel <bjorn.topel@intel.com>
Link: https://lore.kernel.org/bpf/20201214085127.3960-1-magnus.karlsson@gmail.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>

net/xdp/xsk.c

@@ -772,6 +772,10 @@ static int xsk_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
 		}
 	}
 
+	/* FQ and CQ are now owned by the buffer pool and cleaned up with it. */
+	xs->fq_tmp = NULL;
+	xs->cq_tmp = NULL;
+
 	xs->dev = dev;
 	xs->zc = xs->umem->zc;
 	xs->queue_id = qid;

net/xdp/xsk_buff_pool.c

@@ -75,8 +75,6 @@ struct xsk_buff_pool *xp_create_and_assign_umem(struct xdp_sock *xs,
 
 	pool->fq = xs->fq_tmp;
 	pool->cq = xs->cq_tmp;
-	xs->fq_tmp = NULL;
-	xs->cq_tmp = NULL;
 
 	for (i = 0; i < pool->free_heads_cnt; i++) {
 		xskb = &pool->heads[i];