From: Owen Gu guhuinan@xiaomi.com
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().
Fixes: eb2a86ae8c54 ("USB: UAS: fix disconnect by unplugging a hub") Cc: stable@vger.kernel.org Signed-off-by: Yu Chen chenyu45@xiaomi.com Signed-off-by: Owen Gu guhuinan@xiaomi.com Acked-by: Oliver Neukum oneukum@suse.com --- v4: Add the fix tag, cc stable and acked-by tag v3: Add some commit message. v2: Upon uas_submit_urbs() returning -ENODEV despite successful URB submission, the cmnd is added to the devinfo->cmnd array before exiting uas_queuecommand_lck(). https://lore.kernel.org/linux-usb/20251015153157.11870-1-guhuinan@xiaomi.com... v1: https://lore.kernel.org/linux-usb/20250930045309.21588-1-guhuinan@xiaomi.com... --- --- drivers/usb/storage/uas.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/drivers/usb/storage/uas.c b/drivers/usb/storage/uas.c index 03043d567fa1..02fe411567fa 100644 --- a/drivers/usb/storage/uas.c +++ b/drivers/usb/storage/uas.c @@ -698,6 +698,10 @@ static int uas_queuecommand_lck(struct scsi_cmnd *cmnd) * of queueing, no matter how fatal the error */ if (err == -ENODEV) { + if (cmdinfo->state & (COMMAND_INFLIGHT | DATA_IN_URB_INFLIGHT | + DATA_OUT_URB_INFLIGHT)) + goto out; + set_host_byte(cmnd, DID_NO_CONNECT); scsi_done(cmnd); goto zombie; @@ -711,6 +715,7 @@ static int uas_queuecommand_lck(struct scsi_cmnd *cmnd) uas_add_work(cmnd); }
+out: devinfo->cmnd[idx] = cmnd; zombie: spin_unlock_irqrestore(&devinfo->lock, flags);