[PATCH] xen-netfront: handle NULL returned by xdp_convert_buff_to_frame()

[Alexey Nepomnyashih <sdl@nppct.ru>]

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.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Cc: stable@vger.kernel.org # v5.9+
Fixes: 6c5aa6fc4def ("xen networking: add basic XDP support for xen-netfront")
Signed-off-by: Alexey Nepomnyashih <sdl@nppct.ru>
---
 drivers/net/xen-netfront.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 8425226c09f0..e99561de3cda 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -987,6 +987,10 @@ static u32 xennet_run_xdp(struct netfront_queue *queue, struct page *pdata,
 	case XDP_TX:
 		get_page(pdata);
 		xdpf = xdp_convert_buff_to_frame(xdp);
+		if (unlikely(!xdpf)) {
+			trace_xdp_exception(queue->info->netdev, prog, act);
+			break;
+		}
 		err = xennet_xdp_xmit(queue->info->netdev, 1, &xdpf, 0);
 		if (unlikely(!err))
 			xdp_return_frame_rx_napi(xdpf);
-- 
2.43.0