FAILED: patch "[PATCH] xen-netfront: handle NULL returned by" failed to apply to 5.10-stable tree

The patch below does not apply to the 5.10-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-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x cc3628dcd851ddd8d418bf0c897024b4621ddc92
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025042800-convene-bless-ce4b@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From cc3628dcd851ddd8d418bf0c897024b4621ddc92 Mon Sep 17 00:00:00 2001
From: Alexey Nepomnyashih <[email protected]>
Date: Thu, 17 Apr 2025 12:21:17 +0000
Subject: [PATCH] xen-netfront: handle NULL returned by
xdp_convert_buff_to_frame()

The function xdp_convert_buff_to_frame() may return NULL if it fails to correctly convert the XDP buffer into an XDP frame due to memory constraints, internal errors, or invalid data. Failing to check for NULL may lead to a NULL pointer dereference if the result is used later in processing, potentially causing crashes, data corruption, or undefined behavior.

On XDP redirect failure, the associated page must be released explicitly if it was previously retained via get_page(). Failing to do so may result in a memory leak, as the pages reference count is not decremented.

index fc52d5c4c69b..5091e1fa4a0d 100644
@@ -985,20 +985,27 @@ static u32 xennet_run_xdp(struct netfront_queue *queue, struct page *pdata,
 	act = bpf_prog_run_xdp(prog, xdp);
 	switch (act) {
 	case XDP_TX:
-		get_page(pdata);
 		xdpf = xdp_convert_buff_to_frame(xdp);
-		err = xennet_xdp_xmit(queue->info->netdev, 1, &xdpf, 0);
-		if (unlikely(!err))
-			xdp_return_frame_rx_napi(xdpf);
-		else if (unlikely(err < 0))
+		if (unlikely(!xdpf)) {
 			trace_xdp_exception(queue->info->netdev, prog, act);
+			break;
+		}
+		get_page(pdata);
+		err = xennet_xdp_xmit(queue->info->netdev, 1, &xdpf, 0);
+		if (unlikely(err <= 0)) {
+			if (err < 0)
+				trace_xdp_exception(queue->info->netdev, prog, act);
+			xdp_return_frame_rx_napi(xdpf);
+		}
 		break;
 	case XDP_REDIRECT:
 		get_page(pdata);
 		err = xdp_do_redirect(queue->info->netdev, xdp, prog);
 		*need_xdp_flush = true;
-		if (unlikely(err))
+		if (unlikely(err)) {
 			trace_xdp_exception(queue->info->netdev, prog, act);
+			xdp_return_buff(xdp);
+		}
 		break;
 	case XDP_PASS:
 	case XDP_DROP: