CVE-2025-68331

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

usb: uas: fix urb unmapping issue when the uas device is remove during ongoing data transfer

When a UAS device is unplugged during data transfer, there is a probability of a system panic occurring. The root cause is an access to an invalid memory address during URB callback handling. Specifically, this happens when the dma_direct_unmap_sg() function is called within the usb_hcd_unmap_urb_for_dma() interface, but the sg->dma_address field is 0 and the sg data structure has already been freed.

The SCSI driver sends transfer commands by invoking uas_queuecommand_lck() in uas.c, using the uas_submit_urbs() function to submit requests to USB. Within the uas_submit_urbs() implementation, three URBs (sense_urb, data_urb, and cmd_urb) are sequentially submitted. Device removal may occur at any point during uas_submit_urbs execution, which may result in URB submission failure. However, some URBs might have been successfully submitted before the failure, and uas_submit_urbs will return the -ENODEV error code in this case. The current error handling directly calls scsi_done(). In the SCSI driver, this eventually triggers scsi_complete() to invoke scsi_end_request() for releasing the sgtable. The successfully submitted URBs, when being unlinked to giveback, call usb_hcd_unmap_urb_for_dma() in hcd.c, leading to exceptions during sg unmapping operations since the sg data structure has already been freed.

This patch modifies the error condition check in the uas_submit_urbs() function. When a UAS device is removed but one or more URBs have already been successfully submitted to USB, it avoids immediately invoking scsi_done() and save the cmnd to devinfo->cmnd array. If the successfully submitted URBs is completed before devinfo->resetting being set, then the scsi_done() function will be called within uas_try_complete() after all pending URB operations are finalized. Otherwise, the scsi_done() function will be called within uas_zap_pending(), which is executed after usb_kill_anchored_urbs().

The error handling only takes effect when uas_queuecommand_lck() calls uas_submit_urbs() and returns the error value -ENODEV . In this case, the device is disconnected, and the flow proceeds to uas_disconnect(), where uas_zap_pending() is invoked to call uas_try_complete().

Affected Software

References

• https://git.kernel.org/stable/c/26d56a9fcb2014b99e654127960aa0a48a391e3c
• https://git.kernel.org/stable/c/2b90a8131c83f6f2be69397d2b7d14d217d95d2f
• https://git.kernel.org/stable/c/426edbfc88b22601ea34a441a469092e7b301c52
• https://git.kernel.org/stable/c/6289fc489e94c9beb6be2b502ccc263663733d72
• https://git.kernel.org/stable/c/66ac05e7b0d6bbd1bee9fcf729e20fd4cce86d17
• https://git.kernel.org/stable/c/75f8e2643085db4f7e136fc6b368eb114dd80a64
• https://git.kernel.org/stable/c/e3a55221f4de080cb7a91ba10f01c4f708603f8d