This is a note to let you know that I've just added the patch titled
usb: gadget: u_serial: Avoid spinlock recursion in __gs_console_push
to the 5.10-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-gadget-u_serial-avoid-spinlock-recursion-in-__gs.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit ca5a1f67510fb72c0eec85d0dc62f9fea5896e98
Author: Prashanth K <quic_prashk@xxxxxxxxxxx>
Date: Tue May 9 18:57:52 2023 +0530
usb: gadget: u_serial: Avoid spinlock recursion in __gs_console_push
[ Upstream commit e5990469943c711cb00bfde6338d2add6c6d0bfe ]
When serial console over USB is enabled, gs_console_connect
queues gs_console_work, where it acquires the spinlock and
queues the usb request, and this request goes to gadget layer.
Now consider a situation where gadget layer prints something
to dmesg, this will eventually call gs_console_write() which
requires cons->lock. And this causes spinlock recursion. Avoid
this by excluding usb_ep_queue from the spinlock.
spin_lock_irqsave //needs cons->lock
gs_console_write
.
.
_printk
__warn_printk
dev_warn/pr_err
.
.
[USB Gadget Layer]
.
.
usb_ep_queue
gs_console_work
__gs_console_push // acquires cons->lock
process_one_work
Signed-off-by: Prashanth K <quic_prashk@xxxxxxxxxxx>
Link: https://lore.kernel.org/r/1683638872-6885-1-git-send-email-quic_prashk@xxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c
index 3b5a6430e2418..a717b53847a8e 100644
--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -917,8 +917,11 @@ static void __gs_console_push(struct gs_console *cons)
}
req->length = size;
+
+ spin_unlock_irq(&cons->lock);
if (usb_ep_queue(ep, req, GFP_ATOMIC))
req->length = 0;
+ spin_lock_irq(&cons->lock);
}
static void gs_console_work(struct work_struct *work)
