[PATCH AUTOSEL 5.4 22/28] usb: core: usb_submit_urb: downgrade type check

[Sasha Levin <sashal@kernel.org>]

From: Oliver Neukum <oneukum@suse.com>

[ Upstream commit 503bbde34cc3dd2acd231f277ba70c3f9ed22e59 ]

Checking for the endpoint type is no reason for a WARN, as that can
cause a reboot. A driver not checking the endpoint type must not cause a
reboot, as there is just no point in this.  We cannot prevent a device
from doing something incorrect as a reaction to a transfer. Hence
warning for a mere assumption being wrong is not sensible.

Signed-off-by: Oliver Neukum <oneukum@suse.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://lore.kernel.org/r/20250612122149.2559724-1-oneukum@suse.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

LLM Generated explanations, may be completely bogus:

Based on my analysis of this commit, here is my determination:

**Backport Status: YES**

This commit should be backported to stable kernel trees for the
following reasons:

1. **Fixes a real issue that affects users**: The commit addresses a
   problem where a `dev_WARN()` can cause system reboots when
   `panic_on_warn` is enabled. This is a serious issue because a driver
   bug (not checking endpoint types properly) should not be able to
   crash the entire system.

2. **Small and contained fix**: The change is minimal - it only replaces
   `dev_WARN()` with `dev_warn_once()` on line 503 of
   drivers/usb/core/urb.c. This is a one-line change that doesn't affect
   any other functionality.

3. **Clear side effects**: The only behavioral change is that:
   - The warning will no longer trigger a kernel panic when
     `panic_on_warn` is set
   - The warning will only be printed once instead of potentially
     multiple times
   - No backtrace will be generated

4. **No architectural changes**: This is a simple logging level change
   that doesn't modify any USB subsystem architecture or functionality.

5. **Affects critical kernel subsystem**: While USB is a critical
   subsystem, this change actually makes it more stable by preventing
   potential system crashes.

6. **Follows stable tree rules**: This is clearly a bugfix that improves
   system stability. The commit message explicitly states that "A driver
   not checking the endpoint type must not cause a reboot" - this is a
   stability improvement that prevents denial-of-service scenarios.

7. **Similar fixes in the kernel**: There's precedent for this type of
   fix, as shown by commit 281cb9d65a95 ("bnxt_en: Make PTP timestamp
   HWRM more silent") which made a similar conversion from
   `netdev_WARN_ONCE()` to `netdev_warn_once()` for the same reason.

The key insight from the code is that `dev_WARN()` calls `WARN()` which
can trigger a kernel panic if `panic_on_warn` is set. This means a
malicious or buggy USB device could potentially crash the system just by
triggering this warning. Converting to `dev_warn_once()` maintains the
diagnostic value while removing the crash risk.

 drivers/usb/core/urb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/core/urb.c b/drivers/usb/core/urb.c
index 850d0fffe1c6..e60f4ef06e3d 100644
--- a/drivers/usb/core/urb.c
+++ b/drivers/usb/core/urb.c
@@ -490,7 +490,7 @@ int usb_submit_urb(struct urb *urb, gfp_t mem_flags)
 
 	/* Check that the pipe's type matches the endpoint's type */
 	if (usb_pipe_type_check(urb->dev, urb->pipe))
-		dev_WARN(&dev->dev, "BOGUS urb xfer, pipe %x != type %x\n",
+		dev_warn_once(&dev->dev, "BOGUS urb xfer, pipe %x != type %x\n",
 			usb_pipetype(urb->pipe), pipetypes[xfertype]);
 
 	/* Check against a simple/standard policy */
-- 
2.39.5