In raw_release(), when unregister == true, there are two kref_put() calls:
1. Inside the unregister block (extra)
2. At out_put label

The refcount increments are:
- 1 ref from dev_new() in raw_open()
- 1 ref from kref_get() in raw_ioctl_run()

Total: 2 references.

The original code performed 3 kref_put() operations, which causes the refcount
to drop below zero and leads to a double free in dev_free().

Remove the extra kref_put() inside the unregister block to balance the
reference counter correctly.

Since the extra kref_put() triggers an immediate use-after-free condition
on the dev structure, KASAN reports a double-free instead of a refcount warning.

BUG: KASAN: double-free in dev_free+0x424/0x740
Fixes: f2c2e717642c ("usb: gadget: add raw-gadget interface")
Reported-by: syzbot+25612fe5ab3dcafc3aab@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/69c401ad.a70a0220.23629d.0000.GAE@google.com/
Signed-off-by: cuiyudong <cuiyudong@kylinos.cn>
---
 drivers/usb/gadget/legacy/raw_gadget.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/usb/gadget/legacy/raw_gadget.c b/drivers/usb/gadget/legacy/raw_gadget.c
index 4febf8dac7ca..a1fd3fdf1323 100644
--- a/drivers/usb/gadget/legacy/raw_gadget.c
+++ b/drivers/usb/gadget/legacy/raw_gadget.c
@@ -465,12 +465,10 @@ static int raw_release(struct inode *inode, struct file *fd)
 			dev_err(dev->dev,
 				"usb_gadget_unregister_driver() failed with %d\n",
 				ret);
-		/* Matches kref_get() in raw_ioctl_run(). */
-		kref_put(&dev->count, dev_free);
 	}
 
 out_put:
-	/* Matches dev_new() in raw_open(). */
+	/* Matches dev_new() in raw_open() and kref_get() in raw_ioctl_run(). */
 	kref_put(&dev->count, dev_free);
 	return ret;
 }
-- 
2.25.1

On Thu, Mar 26, 2026 at 04:22:45PM +0800, cuiyudong wrote:
> In raw_release(), when unregister == true, there are two kref_put() calls:
> 1. Inside the unregister block (extra)
> 2. At out_put label
> 
> The refcount increments are:
> - 1 ref from dev_new() in raw_open()
> - 1 ref from kref_get() in raw_ioctl_run()
> 
> Total: 2 references.
> 
> The original code performed 3 kref_put() operations, which causes the refcount
> to drop below zero and leads to a double free in dev_free().
> 
> Remove the extra kref_put() inside the unregister block to balance the
> reference counter correctly.
> 
> Since the extra kref_put() triggers an immediate use-after-free condition
> on the dev structure, KASAN reports a double-free instead of a refcount warning.
> 
> BUG: KASAN: double-free in dev_free+0x424/0x740
> Fixes: f2c2e717642c ("usb: gadget: add raw-gadget interface")
> Reported-by: syzbot+25612fe5ab3dcafc3aab@syzkaller.appspotmail.com
> Closes: https://lore.kernel.org/all/69c401ad.a70a0220.23629d.0000.GAE@google.com/
> Signed-off-by: cuiyudong <cuiyudong@kylinos.cn>
> ---
>  drivers/usb/gadget/legacy/raw_gadget.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/gadget/legacy/raw_gadget.c b/drivers/usb/gadget/legacy/raw_gadget.c
> index 4febf8dac7ca..a1fd3fdf1323 100644
> --- a/drivers/usb/gadget/legacy/raw_gadget.c
> +++ b/drivers/usb/gadget/legacy/raw_gadget.c
> @@ -465,12 +465,10 @@ static int raw_release(struct inode *inode, struct file *fd)
>  			dev_err(dev->dev,
>  				"usb_gadget_unregister_driver() failed with %d\n",
>  				ret);
> -		/* Matches kref_get() in raw_ioctl_run(). */
> -		kref_put(&dev->count, dev_free);
>  	}
>  
>  out_put:
> -	/* Matches dev_new() in raw_open(). */
> +	/* Matches dev_new() in raw_open() and kref_get() in raw_ioctl_run(). */
>  	kref_put(&dev->count, dev_free);
>  	return ret;
>  }
> -- 
> 2.25.1
> 
> 

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
to these common problems, but in order to save his sanity (he kept
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  needs to be done here to properly describe this.

If you wish to discuss this problem further, or you have questions about
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