This is a note to let you know that I've just added the patch titled
usb: cdc-wdm: fix reading stuck on device close
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
usb-cdc-wdm-fix-reading-stuck-on-device-close.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 01e01f5c89773c600a9f0b32c888de0146066c3a Mon Sep 17 00:00:00 2001
From: Sergey Ryazanov <ryazanov.s.a@xxxxxxxxx>
Date: Sun, 1 May 2022 20:58:28 +0300
Subject: usb: cdc-wdm: fix reading stuck on device close
From: Sergey Ryazanov <ryazanov.s.a@xxxxxxxxx>
commit 01e01f5c89773c600a9f0b32c888de0146066c3a upstream.
cdc-wdm tracks whether a response reading request is in-progress and
blocks the next request from being sent until the previous request is
completed. As soon as last user closes the cdc-wdm device file, the
driver cancels any ongoing requests, resets the pending response
counter, but leaves the response reading in-progress flag
(WDM_RESPONDING) untouched.
So if the user closes the device file during the response receive
request is being performed, no more data will be obtained from the
modem. The request will be cancelled, effectively preventing the
WDM_RESPONDING flag from being reseted. Keeping the flag set will
prevent a new response receive request from being sent, permanently
blocking the read path. The read path will staying blocked until the
module will be reloaded or till the modem will be re-attached.
This stuck has been observed with a Huawei E3372 modem attached to an
OpenWrt router and using the comgt utility to set up a network
connection.
Fix this issue by clearing the WDM_RESPONDING flag on the device file
close.
Without this fix, the device reading stuck can be easily reproduced in a
few connection establishing attempts. With this fix, a load test for
modem connection re-establishing worked for several hours without any
issues.
Fixes: 922a5eadd5a3 ("usb: cdc-wdm: Fix race between autosuspend and reading from the device")
Signed-off-by: Sergey Ryazanov <ryazanov.s.a@xxxxxxxxx>
Cc: stable <stable@xxxxxxxxxxxxxxx>
Acked-by: Oliver Neukum <oneukum@xxxxxxxx>
Link: https://lore.kernel.org/r/20220501175828.8185-1-ryazanov.s.a@xxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/usb/class/cdc-wdm.c | 1 +
1 file changed, 1 insertion(+)
--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -774,6 +774,7 @@ static int wdm_release(struct inode *ino
poison_urbs(desc);
spin_lock_irq(&desc->iuspin);
desc->resp_count = 0;
+ clear_bit(WDM_RESPONDING, &desc->flags);
spin_unlock_irq(&desc->iuspin);
desc->manage_power(desc->intf, 0);
unpoison_urbs(desc);
Patches currently in stable-queue which might be from ryazanov.s.a@xxxxxxxxx are
queue-5.15/usb-cdc-wdm-fix-reading-stuck-on-device-close.patch
