6.9-stable review patch. If anyone has any objections, please let me know.
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From: Radu Rendec rrendec@redhat.com
[ Upstream commit 9a0c28efeec6383ef22e97437616b920e7320b67 ]
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: 271e015b9153 ("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 Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/ethernet/renesas/rswitch.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/net/ethernet/renesas/rswitch.c b/drivers/net/ethernet/renesas/rswitch.c index dcab638c57fe8..24c90d8f5a442 100644 --- a/drivers/net/ethernet/renesas/rswitch.c +++ b/drivers/net/ethernet/renesas/rswitch.c @@ -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; }