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net: skbuff: don't touch shared zerocopy state in skb_tx_error()

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skb_tx_error() completes the zerocopy uarg and clears
SKBFL_ALL_ZEROCOPY, and skb_zcopy_downgrade_managed() clears
SKBFL_MANAGED_FRAG_REFS. Both live in skb_shinfo(), which every clone
shares, while the caller only owns the reference it is about to drop.
Through a clone it tells the producer its pages are free and drops
SKBFL_SHARED_FRAG for an skb that is still in flight.

Open vSwitch reaches this with a non-last OVS_ACTION_ATTR_RECIRC:
clone_execute() sends a skb_clone() into ovs_dp_process_packet() while
do_execute_actions() keeps forwarding the original, and skb_clone()
does not privatise the frags here -- skb_orphan_frags() returns early
on SKBFL_DONT_ORPHAN. A flow miss on the clone then strips the marker
from the packet still being forwarded, and a later local ESP delivery
decrypts in place over frags it does not own privately.

Skip it for a cloned skb. Nothing is lost: skb_release_data() clears
the zerocopy state once the last reference to the shared data goes.

Fixes: 25121173f7 ("skb: api to report errors for zero copy skbs")
Cc: stable@vger.kernel.org
Suggested-by: Ilya Maximets <i.maximets@ovn.org>
Signed-off-by: Norbert Szetei <norbert@doyensec.com>
Reviewed-by: Ilya Maximets <i.maximets@ovn.org>
Tested-by: Jongmin Jang <payload.jang@gmail.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/CFAB292A-674B-4C14-BB2C-BB8830AD5659@doyensec.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Norbert Szetei 2026-08-22 11:15:08 +02:00 committed by Paolo Abeni
parent 8ece906150
commit f66bdb1cc0
1 changed files with 4 additions and 1 deletions
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5
net/core/skbuff.c
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@ -1417,10 +1417,13 @@ EXPORT_SYMBOL(skb_dump);
*
* Report xmit error if a device callback is tracking this skb.
* skb must be freed afterwards.
*
* Does nothing for a cloned skb: the zerocopy state lives in
* skb_shinfo(), which the clones share.
*/
void skb_tx_error(struct sk_buff *skb)
{
if (skb) {
if (skb && !skb_cloned(skb)) {
skb_zcopy_downgrade_managed(skb);
skb_zcopy_clear(skb, true);
}