From: Kent Gibson <warthog618@gmail.com>
To: Bartosz Golaszewski <brgl@bgdev.pl>
Cc: Linus Walleij <linus.walleij@linaro.org>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Viresh Kumar <viresh.kumar@linaro.org>,
linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] gpio: cdev: fix a crash on line-request release
Date: Wed, 24 May 2023 10:09:42 +0800 [thread overview]
Message-ID: <ZG1x5pcyTN2Fio4J@sol> (raw)
In-Reply-To: <ZG1TLBsOy4mZQlW3@sol>
On Wed, May 24, 2023 at 07:58:36AM +0800, Kent Gibson wrote:
> On Tue, May 23, 2023 at 05:51:01PM +0200, Bartosz Golaszewski wrote:
> > When a GPIO device is forcefully unregistered, we are left with an
> > inactive object. If user-space kept an open file descriptor to a line
> > request associated with such a structure, upon closing it, we'll see the
> > kernel crash due to freeing unexistent GPIO descriptors.
> >
>
> > @@ -1565,17 +1571,21 @@ static ssize_t linereq_read(struct file *file, char __user *buf,
> >
> > static void linereq_free(struct linereq *lr)
> > {
> > + struct gpio_device *gdev = lr->gdev;
> > unsigned int i;
> >
> > for (i = 0; i < lr->num_lines; i++) {
> > if (lr->lines[i].desc) {
> > edge_detector_stop(&lr->lines[i]);
> > - gpiod_free(lr->lines[i].desc);
> > + down_write(&gdev->sem);
> > + if (gdev->chip)
> > + gpiod_free(lr->lines[i].desc);
> > + up_write(&gdev->sem);
Ummm, taking another look at the oops I sent you, the crash actually
occurs in edge_detector_stop():
May 23 11:47:06 firefly kernel: [ 4216.877056] Call Trace:
May 23 11:47:06 firefly kernel: [ 4216.877512] <TASK>
May 23 11:47:06 firefly kernel: [ 4216.877924] irq_domain_deactivate_irq+0x19/0x30
May 23 11:47:06 firefly kernel: [ 4216.878543] free_irq+0x257/0x360
May 23 11:47:06 firefly kernel: [ 4216.879056] linereq_free+0x9b/0xe0
May 23 11:47:06 firefly kernel: [ 4216.879608] linereq_release+0xc/0x20
May 23 11:47:06 firefly kernel: [ 4216.880230] __fput+0x87/0x240
May 23 11:47:06 firefly kernel: [ 4216.880744] task_work_run+0x54/0x80
That free_irq() call is in edge_detector_stop() (which apparently is inlined),
not in gpiod_free().
So pretty sure this patch doesn't even solve my problem, but I will test
it to confirm.
Cheers,
Kent.
next prev parent reply other threads:[~2023-05-24 2:09 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-23 15:51 [PATCH] gpio: cdev: fix a crash on line-request release Bartosz Golaszewski
2023-05-23 23:58 ` Kent Gibson
2023-05-24 2:09 ` Kent Gibson [this message]
2023-05-24 4:36 ` Kent Gibson
2023-05-24 19:42 ` Bartosz Golaszewski
2023-05-25 2:47 ` Kent Gibson
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