CVE-2024-57981

In the Linux kernel, the following vulnerability has been resolved:

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.

This vulnerability is rated as Moderate severity for Red Hat Enterprise Linux because triggering the kernel crash requires local access, such as connecting a specialized physical USB peripheral or manipulating an emulated device within a virtualized guest. The impact is limited to a denial of service via a kernel panic, with no mechanism for privilege escalation or loss of system confidentiality and integrity. Standard enterprise environments typically restrict physical port access, substantially limiting exposure on bare-metal deployments.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.