Commit 968be23c authored by Magnus Karlsson's avatar Magnus Karlsson Committed by Daniel Borkmann
Browse files

xsk: Fix possible segfault at xskmap entry insertion 



Fix possible segfault when entry is inserted into xskmap. This can
happen if the socket is in a state where the umem has been set up, the
Rx ring created but it has yet to be bound to a device. In this case
the pool has not yet been created and we cannot reference it for the
existence of the fill ring. Fix this by removing the whole
xsk_is_setup_for_bpf_map function. Once upon a time, it was used to
make sure that the Rx and fill rings where set up before the driver
could call xsk_rcv, since there are no tests for the existence of
these rings in the data path. But these days, we have a state variable
that we test instead. When it is XSK_BOUND, everything has been set up
correctly and the socket has been bound. So no reason to have the
xsk_is_setup_for_bpf_map function anymore.

Fixes: 7361f9c3 ("xsk: Move fill and completion rings to buffer pool")
Reported-by: default avatar <syzbot+febe51d44243fbc564ee@syzkaller.appspotmail.com>
Signed-off-by: default avatarMagnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/1599037569-26690-1-git-send-email-magnus.karlsson@intel.com
parent 53ea2076

net/xdp/xsk.c

+0 −6
Original line number Diff line number Diff line
@@ -33,12 +33,6 @@ 


static DEFINE_PER_CPU(struct list_head, xskmap_flush_list);



bool xsk_is_setup_for_bpf_map(struct xdp_sock *xs)

{

	return READ_ONCE(xs->rx) &&  READ_ONCE(xs->umem) &&

		(xs->pool->fq || READ_ONCE(xs->fq_tmp));

}



void xsk_set_rx_need_wakeup(struct xsk_buff_pool *pool)

{

	if (pool->cached_need_wakeup & XDP_WAKEUP_RX)

net/xdp/xsk.h

+0 −1
Original line number Diff line number Diff line
@@ -39,7 +39,6 @@ static inline struct xdp_sock *xdp_sk(struct sock *sk) 
	return (struct xdp_sock *)sk;

}



bool xsk_is_setup_for_bpf_map(struct xdp_sock *xs);

void xsk_map_try_sock_delete(struct xsk_map *map, struct xdp_sock *xs,

			     struct xdp_sock **map_entry);

int xsk_map_inc(struct xsk_map *map);

net/xdp/xskmap.c

+0 −5
Original line number Diff line number Diff line
@@ -185,11 +185,6 @@ static int xsk_map_update_elem(struct bpf_map *map, void *key, void *value, 


	xs = (struct xdp_sock *)sock->sk;



	if (!xsk_is_setup_for_bpf_map(xs)) {

		sockfd_put(sock);

		return -EOPNOTSUPP;

	}



	map_entry = &m->xsk_map[i];

	node = xsk_map_node_alloc(m, map_entry);

	if (IS_ERR(node)) {