netdev - [PATCH bpf 1/2] Revert "xsk: support redirect to any socket bound to the same umem"

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Date: Tue,  4 Jun 2024 14:29:25 +0200
From: Magnus Karlsson <magnus.karlsson@...il.com>
To: magnus.karlsson@...el.com,
	bjorn@...nel.org,
	ast@...nel.org,
	daniel@...earbox.net,
	netdev@...r.kernel.org,
	maciej.fijalkowski@...el.com,
	bpf@...r.kernel.org
Cc: YuvalE@...ware.com
Subject: [PATCH bpf 1/2] Revert "xsk: support redirect to any socket bound to the same umem"

From: Magnus Karlsson <magnus.karlsson@...el.com>

This reverts commit 2863d665ea41282379f108e4da6c8a2366ba66db.

This patch introduced a potential kernel crash when multiple napi
instances redirect to the same AF_XDP socket. By removing the
queue_index check, it is possible for multiple napi instances to
access the Rx ring at the same time, which will result in a corrupted
ring state which can lead to a crash when flushing the rings in
__xsk_flush(). This can happen when the linked list of sockets to
flush gets corrupted by concurrent accesses. A quick and small fix is
not possible, so let us revert this for now.

Reported-by: Yuval El-Hanany <YuvalE@...ware.com>
Signed-off-by: Magnus Karlsson <magnus.karlsson@...el.com>
Link: https://lore.kernel.org/xdp-newbies/8100DBDC-0B7C-49DB-9995-6027F6E63147@radware.com/
---
 net/xdp/xsk.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 727aa20be4bd..7d1c0986f9bb 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -313,13 +313,10 @@ static bool xsk_is_bound(struct xdp_sock *xs)
 
 static int xsk_rcv_check(struct xdp_sock *xs, struct xdp_buff *xdp, u32 len)
 {
-	struct net_device *dev = xdp->rxq->dev;
-	u32 qid = xdp->rxq->queue_index;
-
 	if (!xsk_is_bound(xs))
 		return -ENXIO;
 
-	if (!dev->_rx[qid].pool || xs->umem != dev->_rx[qid].pool->umem)
+	if (xs->dev != xdp->rxq->dev || xs->queue_id != xdp->rxq->queue_index)
 		return -EINVAL;
 
 	if (len > xsk_pool_get_rx_frame_size(xs->pool) && !xs->sg) {
-- 
2.45.1