linux-kernel - [PATCH v2] usb: uas: fix urb unmapping issue when the uas device is remove during ongoing data transfer

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Message-ID: <20251015153157.11870-1-guhuinan@xiaomi.com>
Date: Wed, 15 Oct 2025 23:31:57 +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>, Michal Pecio
	<michal.pecio@...il.com>
Subject: [PATCH v2] usb: uas: 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 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 uas_zap_pending() iterates over
devinfo->cmnd array, invoking uas_try_complete() for each command to
finalize their handling.

Signed-off-by: Yu Chen <chenyu45@...omi.com>
Signed-off-by: Owen Gu <guhuinan@...omi.com>
---
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().
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 4ed0dc19afe0..45b01df364f7 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);
-- 
2.43.0