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SubjectRe: [PATCH 3/5 v2] drivers/hid/hid-roccat.c: eliminate a null pointer dereference
On Sat, 29 Oct 2011, Julia Lawall wrote:

> From: Julia Lawall <julia@diku.dk>
>
> It is not possible to take the lock in device if device is NULL.
> The mutex_lock is thus moved after the NULL test, and the relevant part of
> the shared error handling code is moved up.
>
> The semantic match that finds this problem is as follows:
> (http://coccinelle.lip6.fr/)
>
> // <smpl>
> @r@
> expression E, E1;
> identifier f;
> statement S1,S2,S3;
> @@
>
> if (E == NULL)
> {
> ... when != if (E == NULL || ...) S1 else S2
> when != E = E1
> *E->f
> ... when any
> return ...;
> }
> else S3
> // </smpl>
>
> Signed-off-by: Julia Lawall <julia@diku.dk>
>
> ---
> mutex_lock changed to mutex_unlock in error handling code
>
> drivers/hid/hid-roccat.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/hid/hid-roccat.c b/drivers/hid/hid-roccat.c
> index 2596321..36a28b8 100644
> --- a/drivers/hid/hid-roccat.c
> +++ b/drivers/hid/hid-roccat.c
> @@ -163,14 +163,15 @@ static int roccat_open(struct inode *inode, struct file *file)
>
> device = devices[minor];
>
> - mutex_lock(&device->readers_lock);
> -
> if (!device) {
> pr_emerg("roccat device with minor %d doesn't exist\n", minor);
> - error = -ENODEV;
> - goto exit_err;
> + kfree(reader);
> + mutex_unlock(&devices_lock);
> + return -ENODEV;
> }
>
> + mutex_lock(&device->readers_lock);
> +
> if (!device->open++) {
> /* power on device on adding first reader */
> error = hid_hw_power(device->hid, PM_HINT_FULLON);

Julia,

thanks a lot for fixing this.

Could you please redo the patch in a way that it adds second
'exit_unlock1' label (and renames 'exit_unlock' to 'exit_unlock2') (or
any appropriate variation of the names) and preserve error path using goto
instead of mixture of returns and gotos that this patch would introduce?

Thanks,

--
Jiri Kosina
SUSE Labs


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