Re: [PATCH 4.19 108/125] USB: yurex: Fix bad gfp argument

Pavel Machek
2020-09-02T12:58:39Z

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Hi!

> The syzbot fuzzer identified a bug in the yurex driver: It passes
> GFP_KERNEL as a memory-allocation flag to usb_submit_urb() at a time
> when its state is TASK_INTERRUPTIBLE, not TASK_RUNNING:

Yeah, and instead of fixing the bug, patch papers over it, reducing
reliability of the driver in the process.

> This patch changes the call to use GFP_ATOMIC instead of GFP_KERNEL.

Fixing it properly should be as simple as moving prepare_to_wait down,
no?

Signed-off-by: Pavel Machek (CIP) <pavel@denx.de>

diff --git a/drivers/usb/misc/yurex.c b/drivers/usb/misc/yurex.c
index 785080f79073..5fbbb57e6e95 100644
--- a/drivers/usb/misc/yurex.c
+++ b/drivers/usb/misc/yurex.c
@@ -489,10 +489,10 @@ static ssize_t yurex_write(struct file *file, const char __user *user_buffer,
}

/* send the data as the control msg */
- prepare_to_wait(&dev->waitq, &wait, TASK_INTERRUPTIBLE);
dev_dbg(&dev->interface->dev, "%s - submit %c\n", __func__,
dev->cntl_buffer[0]);
- retval = usb_submit_urb(dev->cntl_urb, GFP_ATOMIC);
+ retval = usb_submit_urb(dev->cntl_urb, GFP_KERNEL);
+ prepare_to_wait(&dev->waitq, &wait, TASK_INTERRUPTIBLE);
if (retval >= 0)
timeout = schedule_timeout(YUREX_WRITE_TIMEOUT);
finish_wait(&dev->waitq, &wait);

Best regards,
Pavel

--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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