FAILED: patch "[PATCH] net: skbuff: don't skb_tx_error() the source skb in" failed to apply to 6.18-stable tree

The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x 8ece906150128d5ec2462aabcc978c568433eca4
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026090319-gonad-edge-05ea@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 8ece906150128d5ec2462aabcc978c568433eca4 Mon Sep 17 00:00:00 2001
From: Norbert Szetei <[email protected]>
Date: Sat, 22 Aug 2026 11:13:47 +0200
Subject: [PATCH] net: skbuff: don't skb_tx_error() the source skb in
skb_zerocopy()

skb_zerocopy() copies frags from @from into @to. On an skb_orphan_frags() failure it calls skb_tx_error(@from), a destructive operation on the source skb the copy helper does not own. That completes @from's zerocopy uarg and clears SKBFL_ALL_ZEROCOPY, including the SKBFL_SHARED_FRAG page-ownership marker.

Both callers already report the failure on their own drop path. nfnetlink_queue does it at nla_put_failure, and Open vSwitch does it in the flow-miss drop arm of ovs_dp_process_packet(), so nothing is lost by dropping it here.

On Open vSwitch's OVS_ACTION_ATTR_USERSPACE path the skb is not freed on this error: do_execute_actions() ignores output_userspace()'s return value and, unless the upcall was the last action, keeps forwarding the same skb through the flow's remaining actions. The uarg is completed while that skb is still in flight, telling the producer its buffers are free, and SKBFL_SHARED_FRAG is cleared on an skb the rest of the stack still handles. That flag is what makes esp_input() call skb_cow_data() instead of decrypting in place, so a later local ESP delivery can decrypt over frags the skb does not own privately.

Leave error reporting to the callers.

index d4382b68d56e..ab3d161247b9 100644
@@ -3914,7 +3914,6 @@ skb_zerocopy(struct sk_buff *to, struct sk_buff *from, int len, int hlen)
 	skb_len_add(to, len + plen);
 
 	if (unlikely(skb_orphan_frags(from, GFP_ATOMIC))) {
-		skb_tx_error(from);
 		if (j > 0)
 			put_page(virt_to_head_page(from->head));
 		return -ENOMEM;

From: Norbert Szetei <[email protected]>

[ Upstream commit 8ece906150128d5ec2462aabcc978c568433eca4 ]

skb_zerocopy() copies frags from @from into @to. On an skb_orphan_frags() failure it calls skb_tx_error(@from), a destructive operation on the source skb the copy helper does not own. That completes @from's zerocopy uarg and clears SKBFL_ALL_ZEROCOPY, including the SKBFL_SHARED_FRAG page-ownership marker.

Both callers already report the failure on their own drop path. nfnetlink_queue does it at nla_put_failure, and Open vSwitch does it in the flow-miss drop arm of ovs_dp_process_packet(), so nothing is lost by dropping it here.

On Open vSwitch's OVS_ACTION_ATTR_USERSPACE path the skb is not freed on this error: do_execute_actions() ignores output_userspace()'s return value and, unless the upcall was the last action, keeps forwarding the same skb through the flow's remaining actions. The uarg is completed while that skb is still in flight, telling the producer its buffers are free, and SKBFL_SHARED_FRAG is cleared on an skb the rest of the stack still handles. That flag is what makes esp_input() call skb_cow_data() instead of decrypting in place, so a later local ESP delivery can decrypt over frags the skb does not own privately.

Leave error reporting to the callers.

---
 net/core/skbuff.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

index e75baa72a22e3..133cd56f7b5e1 100644
@@ -3856,10 +3856,9 @@ skb_zerocopy(struct sk_buff *to, struct sk_buff *from, int len, int hlen)
 
 	skb_len_add(to, len + plen);
 
-	if (unlikely(skb_orphan_frags(from, GFP_ATOMIC))) {
-		skb_tx_error(from);
+	if (unlikely(skb_orphan_frags(from, GFP_ATOMIC)))
 		return -ENOMEM;
-	}
+
 	skb_zerocopy_clone(to, from, GFP_ATOMIC);
 
 	for (i = 0; i < skb_shinfo(from)->nr_frags; i++) {

2.55.0

Queued for 6.18, thanks.

Thanks,
Sasha