Re: [PATCH net v2 3/3] net: skbuff: don't touch shared zerocopy state in skb_tx_error()
From: Ilya Maximets <i.maximets@ovn.org>
Date: 2026-08-17 16:47:43
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On 8/16/26 8:57 AM, Norbert Szetei wrote:
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: 36d5fe6a0007 ("core, nfqueue, openvswitch: Orphan frags in skb_zerocopy and handle errors")
I think, this should be 25121173f7b1 ("skb: api to report errors for zero
copy skbs") instead.
Otherwise, LGTM.
Also, please, add all maintainers as per get_maintainers script into CC
while sending patches (may drop Zoltan though, since his email bounced,
as well as Pravin).
Note: there is a conflict between this set and the
https://lore.kernel.org/r/20260814191336.187243-1-almasrymina@google.com (local)
But I think, it's better if we apply the tx_error fixes first, as they
need to be backported further.
Best regards, Ilya Maximets.
quoted hunk ↗ jump to hunk
Fixes: f4c50a4034e6 ("xfrm: esp: avoid in-place decrypt on shared skb frags") Cc: stable@vger.kernel.org Suggested-by: Ilya Maximets <i.maximets@ovn.org> Signed-off-by: Norbert Szetei <redacted> --- net/core/skbuff.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)diff --git a/net/core/skbuff.c b/net/core/skbuff.c index db62ed6e04b9..04776a112334 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c@@ -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); }