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net: rswitch: Avoid use-after-free in rswitch_poll()

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The use-after-free is actually in rswitch_tx_free(), which is inlined in
rswitch_poll(). Since `skb` and `gq->skbs[gq->dirty]` are in fact the
same pointer, the skb is first freed using dev_kfree_skb_any(), then the
value in skb->len is used to update the interface statistics.

Let's move around the instructions to use skb->len before the skb is
freed.

This bug is trivial to reproduce using KFENCE. It will trigger a splat
every few packets. A simple ARP request or ICMP echo request is enough.

Fixes: 271e015b91 ("net: rswitch: Add unmap_addrs instead of dma address in each desc")
Signed-off-by: Radu Rendec <rrendec@redhat.com>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Link: https://patch.msgid.link/20240702210838.2703228-1-rrendec@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Radu Rendec 2024-07-02 17:08:37 -04:00 committed by Jakub Kicinski
parent 8eb301bd7b
commit 9a0c28efee
1 changed files with 2 additions and 2 deletions
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4
drivers/net/ethernet/renesas/rswitch.c
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@ -871,13 +871,13 @@ static void rswitch_tx_free(struct net_device *ndev)
dma_rmb();
skb = gq->skbs[gq->dirty];
if (skb) {
rdev->ndev->stats.tx_packets++;
rdev->ndev->stats.tx_bytes += skb->len;
dma_unmap_single(ndev->dev.parent,
gq->unmap_addrs[gq->dirty],
skb->len, DMA_TO_DEVICE);
dev_kfree_skb_any(gq->skbs[gq->dirty]);
gq->skbs[gq->dirty] = NULL;
rdev->ndev->stats.tx_packets++;
rdev->ndev->stats.tx_bytes += skb->len;
}
desc->desc.die_dt = DT_EEMPTY;
}