2012-10-07 09:57:22

by Constantine Shulyupin

Subject: [PATCH] USB: usb-skeleton.c: fix compilation error and restore kref_put on fail in skel_open

From: Constantine Shulyupin <[email protected]>

Function skel_open increments usage count for the device with kref_get and the usage count should be decremented on the function failure.

Some last changes in function skel_open and finally commit
52a7499 Revert "USB: usb-skeleton.c: fix open/disconnect race"
introduced a bug in function skel_open, which this patch fixes.

Signed-off-by: Constantine Shulyupin <[email protected]>
---
drivers/usb/usb-skeleton.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/usb-skeleton.c b/drivers/usb/usb-skeleton.c
index 0616f23..027005b 100644
--- a/drivers/usb/usb-skeleton.c
+++ b/drivers/usb/usb-skeleton.c
@@ -113,8 +113,10 @@ static int skel_open(struct inode *inode, struct file *file)
mutex_lock(&dev->io_mutex);

retval = usb_autopm_get_interface(interface);
- if (retval)
- goto out_err;
+ if (retval) {
+ kref_put(&dev->kref, skel_delete);
+ goto exit;
+ }

/* save our object in the file's private structure */
file->private_data = dev;
--
1.7.9.5

2012-10-10 09:57:31

by Oliver Neukum

Subject: Re: [PATCH] USB: usb-skeleton.c: fix compilation error and restore kref_put on fail in skel_open

On Sunday 07 October 2012 11:57:12 Constantine Shulyupin wrote:
> From: Constantine Shulyupin <[email protected]>
>
> Function skel_open increments usage count for the device with kref_get and the usage count should be decremented on the function failure.
>
> Some last changes in function skel_open and finally commit
> 52a7499 Revert "USB: usb-skeleton.c: fix open/disconnect race"
> introduced a bug in function skel_open, which this patch fixes.
>
> Signed-off-by: Constantine Shulyupin <[email protected]>
> ---
> drivers/usb/usb-skeleton.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/usb-skeleton.c b/drivers/usb/usb-skeleton.c
> index 0616f23..027005b 100644
> --- a/drivers/usb/usb-skeleton.c
> +++ b/drivers/usb/usb-skeleton.c
> @@ -113,8 +113,10 @@ static int skel_open(struct inode *inode, struct file *file)
> mutex_lock(&dev->io_mutex);
>
> retval = usb_autopm_get_interface(interface);
> - if (retval)
> - goto out_err;
> + if (retval) {
> + kref_put(&dev->kref, skel_delete);
> + goto exit;
> + }
>
> /* save our object in the file's private structure */
> file->private_data = dev;

Hi,

good catch, but the fix is wrong. You also need to drop the lock.

Regards
Oliver