CVE-2025-21951 Information

Description

In the Linux kernel the following vulnerability has been resolved:

bus: mhi: host: pci_generic: Use pci_try_reset_function() to avoid deadlock

There are multiple places from where the recovery work gets scheduled asynchronously. Also there are multiple places where the caller waits synchronously for the recovery to be completed. One such place is during the PM shutdown() callback.

If the device is not alive during recovery_work it will try to reset the device using pci_reset_function(). This function internally will take the device_lock() first before resetting the device. By this time if the lock has already been acquired then recovery_work will get stalled while waiting for the lock. And if the lock was already acquired by the caller which waits for the recovery_work to be completed it will lead to deadlock.

This is what happened on the X1E80100 CRD device when the device died before shutdown() callback. Driver core calls the driver’s shutdown() callback while holding the device_lock() leading to deadlock.

And this deadlock scenario can occur on other paths as well like during the PM suspend() callback where the driver core would hold the device_lock() before calling driver’s suspend() callback. And if the recovery_work was already started it could lead to deadlock. This is also observed on the X1E80100 CRD.

So to fix both issues use pci_try_reset_function() in recovery_work. This function first checks for the availability of the device_lock() before trying to reset the device. If the lock is available it will acquire it and reset the device. Otherwise it will return -EAGAIN. If that happens recovery_work will fail with the error message \Recovery failed\ as not much could be done.

Reference

https://git.kernel.org/stable/c/1f9eb7078bc6b5fb5cbfbcb37c4bc01685332b95 https://git.kernel.org/stable/c/62505657475c245c9cd46e42ac01026d1e61f027 https://git.kernel.org/stable/c/7746f3bb8917fccb4571a576f3837d80fc513054 https://git.kernel.org/stable/c/7a5ffadd54fe2662f5c99cdccf30144d060376f7 https://git.kernel.org/stable/c/985d3cf56d8745ca637deee273929e01df449f85 https://git.kernel.org/stable/c/a321d163de3d8aa38a6449ab2becf4b1581aed96