This is a note to let you know that I've just added the patch titled net: ll_temac: Make sure to free skb when it is completely used to the 5.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: net-ll_temac-make-sure-to-free-skb-when-it-is-completely-used.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 6aa32217a9a446275440ee8724b1ecaf1838df47 Mon Sep 17 00:00:00 2001 From: Esben Haabendal <esben@xxxxxxxxxx> Date: Fri, 18 Jun 2021 12:52:23 +0200 Subject: net: ll_temac: Make sure to free skb when it is completely used From: Esben Haabendal <esben@xxxxxxxxxx> commit 6aa32217a9a446275440ee8724b1ecaf1838df47 upstream. With the skb pointer piggy-backed on the TX BD, we have a simple and efficient way to free the skb buffer when the frame has been transmitted. But in order to avoid freeing the skb while there are still fragments from the skb in use, we need to piggy-back on the TX BD of the skb, not the first. Without this, we are doing use-after-free on the DMA side, when the first BD of a multi TX BD packet is seen as completed in xmit_done, and the remaining BDs are still being processed. Cc: stable@xxxxxxxxxxxxxxx # v5.4+ Signed-off-by: Esben Haabendal <esben@xxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/net/ethernet/xilinx/ll_temac_main.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) --- a/drivers/net/ethernet/xilinx/ll_temac_main.c +++ b/drivers/net/ethernet/xilinx/ll_temac_main.c @@ -873,7 +873,6 @@ temac_start_xmit(struct sk_buff *skb, st return NETDEV_TX_OK; } cur_p->phys = cpu_to_be32(skb_dma_addr); - ptr_to_txbd((void *)skb, cur_p); for (ii = 0; ii < num_frag; ii++) { if (++lp->tx_bd_tail >= TX_BD_NUM) @@ -912,6 +911,11 @@ temac_start_xmit(struct sk_buff *skb, st } cur_p->app0 |= cpu_to_be32(STS_CTRL_APP0_EOP); + /* Mark last fragment with skb address, so it can be consumed + * in temac_start_xmit_done() + */ + ptr_to_txbd((void *)skb, cur_p); + tail_p = lp->tx_bd_p + sizeof(*lp->tx_bd_v) * lp->tx_bd_tail; lp->tx_bd_tail++; if (lp->tx_bd_tail >= TX_BD_NUM) Patches currently in stable-queue which might be from esben@xxxxxxxxxx are queue-5.4/net-ll_temac-fix-tx-bd-buffer-overwrite.patch queue-5.4/net-ll_temac-make-sure-to-free-skb-when-it-is-completely-used.patch