FAILED: patch "[PATCH] usb: xhci: Fix NULL pointer dereference on certain command" 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 1e0a19912adb68a4b2b74fd77001c96cd83eb073
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025020457-imprecise-rectify-1264@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From 1e0a19912adb68a4b2b74fd77001c96cd83eb073 Mon Sep 17 00:00:00 2001
From: Michal Pecio <[email protected]>
Date: Fri, 27 Dec 2024 14:01:40 +0200
Subject: [PATCH] usb: xhci: Fix NULL pointer dereference on certain command
aborts

If a command is queued to the final usable TRB of a ring segment, the enqueue pointer is advanced to the subsequent link TRB and no further. If the command is later aborted, when the abort completion is handled the dequeue pointer is advanced to the first TRB of the next segment.

If no further commands are queued, xhci_handle_stopped_cmd_ring() sees the ring pointers unequal and assumes that there is a pending command, so it calls xhci_mod_cmd_timer() which crashes if cur_cmd was NULL.

Don't attempt timer setup if cur_cmd is NULL. The subsequent doorbell ring likely is unnecessary too, but it's harmless. Leave it alone.

This is probably Bug 219532, but no confirmation has been received.

The issue has been independently reproduced and confirmed fixed using a USB MCU programmed to NAK the Status stage of SET_ADDRESS forever. Everything continued working normally after several prevented crashes.

index 09b05a62375e..dfe1a676d487 100644
@@ -422,7 +422,8 @@ static void xhci_handle_stopped_cmd_ring(struct xhci_hcd *xhci,
 	if ((xhci->cmd_ring->dequeue != xhci->cmd_ring->enqueue) &&
 	    !(xhci->xhc_state & XHCI_STATE_DYING)) {
 		xhci->current_cmd = cur_cmd;
-		xhci_mod_cmd_timer(xhci);
+		if (cur_cmd)
+			xhci_mod_cmd_timer(xhci);
 		xhci_ring_cmd_db(xhci);
 	}
 }