Commit 2afd23f7 authored Oct 21, 2019 by Magnus Karlsson Committed by Alexei Starovoitov Oct 23, 2019

xsk: Fix registration of Rx-only sockets

Having Rx-only AF_XDP sockets can potentially lead to a crash in the
system by a NULL pointer dereference in xsk_umem_consume_tx(). This
function iterates through a list of all sockets tied to a umem and
checks if there are any packets to send on the Tx ring. Rx-only
sockets do not have a Tx ring, so this will cause a NULL pointer
dereference. This will happen if you have registered one or more
Rx-only sockets to a umem and the driver is checking the Tx ring even
on Rx, or if the XDP_SHARED_UMEM mode is used and there is a mix of
Rx-only and other sockets tied to the same umem.

Fixed by only putting sockets with a Tx component on the list that
xsk_umem_consume_tx() iterates over.

Fixes: ac98d8aa ("xsk: wire upp Tx zero-copy functions")
Reported-by: Kal Cutter Conley <kal.conley@dectris.com>
Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Link: https://lore.kernel.org/bpf/1571645818-16244-1-git-send-email-magnus.karlsson@intel.com

parent 3b4d9eb2

net/xdp/xdp_umem.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -27,6 +27,9 @@ void xdp_add_sk_umem(struct xdp_umem umem, struct xdp_sock xs)
		{
		unsigned long flags;

		if (!xs->tx)
		return;

		spin_lock_irqsave(&umem->xsk_list_lock, flags);
		list_add_rcu(&xs->list, &umem->xsk_list);
		spin_unlock_irqrestore(&umem->xsk_list_lock, flags);
		@@ -36,6 +39,9 @@ void xdp_del_sk_umem(struct xdp_umem umem, struct xdp_sock xs)
		{
		unsigned long flags;

		if (!xs->tx)
		return;

		spin_lock_irqsave(&umem->xsk_list_lock, flags);
		list_del_rcu(&xs->list);
		spin_unlock_irqrestore(&umem->xsk_list_lock, flags);

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