On Mon, Oct 26, 2026 at 09:16:07AM +0000, Paul Moses wrote:
> Preemptible queues require software padding so hardware includes the
> padding bytes in the mCRC. Padding currently runs after TX timestamp
> reservation takes an extra skb reference. If padding needs to expand
> the skb, pskb_expand_head() rejects the shared skb.
>
> Commit c7d8bc3dd511 ("net: skbuff: don't BUG() on bad arguments to
> pskb_expand_head()") replaced the BUG_ON() with -EINVAL, exposing the
> padding error path. skb_padto() drops one reference on failure, and
> out_drop drops another. This can free the skb while the pending TX
> timestamp still holds its pointer.
>
> Move padding before TX timestamp reservation and use __skb_put_padto()
> with free_on_error set to false so out_drop handles the skb release.
> Preserve the VLAN flags in first->tx_flags when adding timestamp flags.
>
> Fixes: 17643482e9ff ("igc: add preemptible queue support in taprio")
> Signed-off-by: Paul Moses <[email protected]>
I skimmed thru clashiko output and nothing major stands out to me. For
your future contributions - multiple patches sent as change set require to
have the cover letter.
For the series:
Reviewed-by: Maciej Fijalkowski <[email protected]>
> ---
> drivers/net/ethernet/intel/igc/igc_main.c | 39 +++++++++++------------
> 1 file changed, 19 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/igc/igc_main.c
> b/drivers/net/ethernet/intel/igc/igc_main.c
> index 1fb5f3cbe93c..f1bf4e462a51 100644
> --- a/drivers/net/ethernet/intel/igc/igc_main.c
> +++ b/drivers/net/ethernet/intel/igc/igc_main.c
> @@ -1661,6 +1661,23 @@ static netdev_tx_t igc_xmit_frame_ring(struct sk_buff
> *skb,
> goto out_drop;
> }
>
> + if (skb_vlan_tag_present(skb)) {
> + tx_flags |= IGC_TX_FLAGS_VLAN;
> + tx_flags |= (skb_vlan_tag_get(skb) << IGC_TX_FLAGS_VLAN_SHIFT);
> + }
> +
> + /* record initial flags and protocol */
> + first->tx_flags = tx_flags;
> + first->protocol = protocol;
> +
> + /* For preemptible queue, manually pad the skb so that HW includes
> + * padding bytes in mCRC calculation
> + */
> + if (tx_ring->preemptible && skb->len < ETH_ZLEN) {
> + if (__skb_put_padto(skb, ETH_ZLEN, false))
> + goto out_drop;
> + }
> +
> if (unlikely(test_bit(IGC_RING_FLAG_TX_HWTSTAMP, &tx_ring->flags) &&
> skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP)) {
> unsigned long flags;
> @@ -1669,10 +1686,10 @@ static netdev_tx_t igc_xmit_frame_ring(struct sk_buff
> *skb,
> spin_lock_irqsave(&adapter->ptp_tx_lock, flags);
> if (igc_request_tx_tstamp(adapter, skb, &tstamp_flags)) {
> skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
> - tx_flags |= IGC_TX_FLAGS_TSTAMP | tstamp_flags;
> + first->tx_flags |= IGC_TX_FLAGS_TSTAMP | tstamp_flags;
> if (skb->sk &&
> READ_ONCE(skb->sk->sk_tsflags) &
> SOF_TIMESTAMPING_BIND_PHC)
> - tx_flags |= IGC_TX_FLAGS_TSTAMP_TIMER_1;
> + first->tx_flags |= IGC_TX_FLAGS_TSTAMP_TIMER_1;
> } else {
> adapter->tx_hwtstamp_skipped++;
> }
> @@ -1680,24 +1697,6 @@ static netdev_tx_t igc_xmit_frame_ring(struct sk_buff
> *skb,
> spin_unlock_irqrestore(&adapter->ptp_tx_lock, flags);
> }
>
> - if (skb_vlan_tag_present(skb)) {
> - tx_flags |= IGC_TX_FLAGS_VLAN;
> - tx_flags |= (skb_vlan_tag_get(skb) << IGC_TX_FLAGS_VLAN_SHIFT);
> - }
> -
> - /* record initial flags and protocol */
> - first->tx_flags = tx_flags;
> - first->protocol = protocol;
> -
> - /* For preemptible queue, manually pad the skb so that HW includes
> - * padding bytes in mCRC calculation
> - */
> - if (tx_ring->preemptible && skb->len < ETH_ZLEN) {
> - if (skb_padto(skb, ETH_ZLEN))
> - goto out_drop;
> - skb_put(skb, ETH_ZLEN - skb->len);
> - }
> -
> tso = igc_tso(tx_ring, first, launch_time, first_flag, &hdr_len);
> if (tso < 0)
> goto out_drop;
>
> base-commit: af32da41b0327b9c6a37856ba82b6760d6c8d10e
>
>
