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 7576920e2d5a..9f202f575cec 100644 --- a/drivers/usb/core/urb.c +++ b/drivers/usb/core/urb.c @@ -500,7 +500,7 @@ 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 */