[PATCH] fix urb unmapping issue when the uas device is remove during ongoing data transfer

[guhuinan]

From: Owen Gu <guhu...@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 completed (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(). Instead, it waits for the successfully submitted URBs to
complete , and then triggers the scsi_done() function call within
uas_try_complete() after all pending URB operations are finalized.

Signed-off-by: Yu Chen <chen...@xiaomi.com>
Signed-off-by: Owen Gu <guhu...@xiaomi.com>
---
drivers/usb/storage/uas.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/storage/uas.c b/drivers/usb/storage/uas.c
index 4ed0dc19afe0..6bfc7281f7ad 100644
--- a/drivers/usb/storage/uas.c
+++ b/drivers/usb/storage/uas.c
@@ -699,7 +699,9 @@ static int uas_queuecommand_lck(struct scsi_cmnd *cmnd)
*/
if (err == -ENODEV) {
set_host_byte(cmnd, DID_NO_CONNECT);
- scsi_done(cmnd);
+ if (!(cmdinfo->state & (COMMAND_INFLIGHT | DATA_IN_URB_INFLIGHT |
+ DATA_OUT_URB_INFLIGHT)))
+ scsi_done(cmnd);
goto zombie;
}
if (err) {
--
2.43.0

[Oliver Neukum]

Hi,

Why then set the host byte unconditionally?

> - scsi_done(cmnd);
> + if (!(cmdinfo->state & (COMMAND_INFLIGHT | DATA_IN_URB_INFLIGHT |
> + DATA_OUT_URB_INFLIGHT)))
> + scsi_done(cmnd);

It would seem to me that in this case you need to make sure
in the completion handlers that scsi_done() is always called,
even if the resetting flag is set.

Regards
Oliver