* [PATCH] char: pcmcia: scr24x_cs: Fix use-after-free in scr24x_fops
@ 2022-09-16 5:00 Hyunwoo Kim
2022-09-16 6:59 ` Arnd Bergmann
0 siblings, 1 reply; 3+ messages in thread
From: Hyunwoo Kim @ 2022-09-16 5:00 UTC (permalink / raw)
To: lkundrak, arnd, gregkh; +Cc: linux-kernel, imv4bel
A race condition may occur if the user physically removes the
pcmcia device while calling open() for this char device node.
This is a race condition between the scr24x_open() function and
the scr24x_remove() function, which may eventually result in UAF.
So, add a mutex to the scr24x_open() and scr24x_remove() functions
to avoid race contidion of krefs.
Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
---
drivers/char/pcmcia/scr24x_cs.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/char/pcmcia/scr24x_cs.c b/drivers/char/pcmcia/scr24x_cs.c
index 1bdce08fae3d..319e8d79048e 100644
--- a/drivers/char/pcmcia/scr24x_cs.c
+++ b/drivers/char/pcmcia/scr24x_cs.c
@@ -76,8 +76,10 @@ static int scr24x_open(struct inode *inode, struct file *filp)
struct scr24x_dev *dev = container_of(inode->i_cdev,
struct scr24x_dev, c_dev);
+ mutex_lock(&dev->lock);
kref_get(&dev->refcnt);
filp->private_data = dev;
+ mutex_unlock(&dev->lock);
return stream_open(inode, filp);
}
@@ -298,9 +300,10 @@ static void scr24x_remove(struct pcmcia_device *link)
cdev_del(&dev->c_dev);
clear_bit(dev->devno, scr24x_minors);
dev->dev = NULL;
- mutex_unlock(&dev->lock);
kref_put(&dev->refcnt, scr24x_delete);
+
+ mutex_unlock(&dev->lock);
}
static const struct pcmcia_device_id scr24x_ids[] = {
--
2.25.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] char: pcmcia: scr24x_cs: Fix use-after-free in scr24x_fops
2022-09-16 5:00 [PATCH] char: pcmcia: scr24x_cs: Fix use-after-free in scr24x_fops Hyunwoo Kim
@ 2022-09-16 6:59 ` Arnd Bergmann
2022-09-16 8:11 ` Hyunwoo Kim
0 siblings, 1 reply; 3+ messages in thread
From: Arnd Bergmann @ 2022-09-16 6:59 UTC (permalink / raw)
To: Hyunwoo Kim, Lubomir Rintel, Greg Kroah-Hartman; +Cc: linux-kernel
On Fri, Sep 16, 2022, at 7:00 AM, Hyunwoo Kim wrote:
> @@ -298,9 +300,10 @@ static void scr24x_remove(struct pcmcia_device *link)
> cdev_del(&dev->c_dev);
> clear_bit(dev->devno, scr24x_minors);
> dev->dev = NULL;
> - mutex_unlock(&dev->lock);
>
> kref_put(&dev->refcnt, scr24x_delete);
> +
> + mutex_unlock(&dev->lock);
> }
This appears to introduce a new use-after-free, when the kref_put()
frees the 'dev' structure and you unlock the mutex in that structure
afterwards.
Arnd
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] char: pcmcia: scr24x_cs: Fix use-after-free in scr24x_fops
2022-09-16 6:59 ` Arnd Bergmann
@ 2022-09-16 8:11 ` Hyunwoo Kim
0 siblings, 0 replies; 3+ messages in thread
From: Hyunwoo Kim @ 2022-09-16 8:11 UTC (permalink / raw)
To: Arnd Bergmann; +Cc: Lubomir Rintel, Greg Kroah-Hartman, linux-kernel, imv4bel
On Fri, Sep 16, 2022 at 08:59:44AM +0200, Arnd Bergmann wrote:
> This appears to introduce a new use-after-free, when the kref_put()
> frees the 'dev' structure and you unlock the mutex in that structure
> afterwards.
yes. Every patch I've submitted has this issue.
I'll replace the mutex with a global variable and submit a v2 patch that fixes other issues.
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2022-09-16 8:11 UTC | newest]
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2022-09-16 5:00 [PATCH] char: pcmcia: scr24x_cs: Fix use-after-free in scr24x_fops Hyunwoo Kim
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2022-09-16 8:11 ` Hyunwoo Kim
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