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

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Message-ID: <20250930045309.21588-1-guhuinan@xiaomi.com>
Date: Tue, 30 Sep 2025 12:53:08 +0800
From: guhuinan <guhuinan@...omi.com>
To: Oliver Neukum <oneukum@...e.com>, Alan Stern <stern@...land.harvard.edu>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC: <linux-usb@...r.kernel.org>, <linux-scsi@...r.kernel.org>,
	<usb-storage@...ts.one-eyed-alien.net>, <linux-kernel@...r.kernel.org>, "Yu
 Chen" <chenyu45@...omi.com>, Owen Gu <guhuinan@...omi.com>
Subject: [PATCH] fix urb unmapping issue when the uas device is remove during ongoing data transfer

From: Owen Gu <guhuinan@...omi.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 <chenyu45@...omi.com>
Signed-off-by: Owen Gu <guhuinan@...omi.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