Commit 968be23c authored Sep 02, 2020 by Magnus Karlsson Committed by Daniel Borkmann Sep 02, 2020

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: <syzbot+febe51d44243fbc564ee@syzkaller.appspotmail.com>
Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: Daniel 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)) {

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