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SubjectRe: [PATCH] bttv: fix mutex use before init
Date
On Tuesday 14 December 2010, Brandon Philips wrote:
> On 17:13 Sun 12 Dec 2010, Torsten Kaiser wrote:
> > * change &fh->cap.vb_lock in bttv_open() AND radio_open() to
> > &btv->init.cap.vb_lock
> > * add a mutex_init(&btv->init.cap.vb_lock) to the setup of init in
> > bttv_probe()
>
> That seems like a reasonable suggestion. An openSUSE user submitted this
> bug to our tracker too. Here is the patch I am having him test.
>
> Would you mind testing it?
>
> From 456dc0ce36db523c4c0c8a269f4eec43a72de1dc Mon Sep 17 00:00:00 2001
> From: Brandon Philips <bphilips@suse.de>
> Date: Mon, 13 Dec 2010 16:21:55 -0800
> Subject: [PATCH] bttv: fix locking for btv->init
>
> Fix locking for the btv->init by using btv->init.cap.vb_lock and in the
> process fix uninitialized deref introduced in c37db91fd0d.
>
> Signed-off-by: Brandon Philips <bphilips@suse.de>
> ---
> drivers/media/video/bt8xx/bttv-driver.c | 24 +++++++++++++-----------
> 1 files changed, 13 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/media/video/bt8xx/bttv-driver.c
> b/drivers/media/video/bt8xx/bttv-driver.c index a529619..e656424 100644
> --- a/drivers/media/video/bt8xx/bttv-driver.c
> +++ b/drivers/media/video/bt8xx/bttv-driver.c
> @@ -2391,16 +2391,11 @@ static int setup_window_lock(struct bttv_fh *fh,
> struct bttv *btv, fh->ov.field = win->field;
> fh->ov.setup_ok = 1;
>
> - /*
> - * FIXME: btv is protected by btv->lock mutex, while btv->init
> - * is protected by fh->cap.vb_lock. This seems to open the
> - * possibility for some race situations. Maybe the better would
> - * be to unify those locks or to use another way to store the
> - * init values that will be consumed by videobuf callbacks
> - */
> + mutex_lock(&btv->init.cap.vb_lock);
> btv->init.ov.w.width = win->w.width;
> btv->init.ov.w.height = win->w.height;
> btv->init.ov.field = win->field;
> + mutex_unlock(&btv->init.cap.vb_lock);
>
> /* update overlay if needed */
> retval = 0;
> @@ -2620,9 +2615,11 @@ static int bttv_s_fmt_vid_cap(struct file *file,
> void *priv, fh->cap.last = V4L2_FIELD_NONE;
> fh->width = f->fmt.pix.width;
> fh->height = f->fmt.pix.height;
> + mutex_lock(&btv->init.cap.vb_lock);
> btv->init.fmt = fmt;
> btv->init.width = f->fmt.pix.width;
> btv->init.height = f->fmt.pix.height;
> + mutex_unlock(&btv->init.cap.vb_lock);
> mutex_unlock(&fh->cap.vb_lock);
>
> return 0;
> @@ -2855,6 +2852,7 @@ static int bttv_s_fbuf(struct file *file, void *f,
>
> retval = 0;
> fh->ovfmt = fmt;
> + mutex_lock(&btv->init.cap.vb_lock);
> btv->init.ovfmt = fmt;
> if (fb->flags & V4L2_FBUF_FLAG_OVERLAY) {
> fh->ov.w.left = 0;
> @@ -2876,6 +2874,7 @@ static int bttv_s_fbuf(struct file *file, void *f,
> retval = bttv_switch_overlay(btv, fh, new);
> }
> }
> + mutex_unlock(&btv->init.cap.vb_lock);
> mutex_unlock(&fh->cap.vb_lock);
> return retval;
> }
> @@ -3141,6 +3140,7 @@ static int bttv_s_crop(struct file *file, void *f,
> struct v4l2_crop *crop) fh->do_crop = 1;
>
> mutex_lock(&fh->cap.vb_lock);
> + mutex_lock(&btv->init.cap.vb_lock);
>
> if (fh->width < c.min_scaled_width) {
> fh->width = c.min_scaled_width;
> @@ -3158,6 +3158,7 @@ static int bttv_s_crop(struct file *file, void *f,
> struct v4l2_crop *crop) btv->init.height = c.max_scaled_height;
> }
>
> + mutex_unlock(&btv->init.cap.vb_lock);
> mutex_unlock(&fh->cap.vb_lock);
>
> return 0;
> @@ -3302,9 +3303,9 @@ static int bttv_open(struct file *file)
> * Let's first copy btv->init at fh, holding cap.vb_lock, and then work
> * with the rest of init, holding btv->lock.
> */
> - mutex_lock(&fh->cap.vb_lock);
> + mutex_lock(&btv->init.cap.vb_lock);
> *fh = btv->init;
> - mutex_unlock(&fh->cap.vb_lock);
> + mutex_unlock(&btv->init.cap.vb_lock);
>
> fh->type = type;
> fh->ov.setup_ok = 0;
> @@ -3502,9 +3503,9 @@ static int radio_open(struct file *file)
> if (unlikely(!fh))
> return -ENOMEM;
> file->private_data = fh;
> - mutex_lock(&fh->cap.vb_lock);
> + mutex_lock(&btv->init.cap.vb_lock);
> *fh = btv->init;
> - mutex_unlock(&fh->cap.vb_lock);
> + mutex_unlock(&btv->init.cap.vb_lock);
>
> mutex_lock(&btv->lock);
> v4l2_prio_open(&btv->prio, &fh->prio);
> @@ -4489,6 +4490,7 @@ static int __devinit bttv_probe(struct pci_dev *dev,
> btv->opt_coring = coring;
>
> /* fill struct bttv with some useful defaults */
> + mutex_init(&btv->init.cap.vb_lock);
> btv->init.btv = btv;
> btv->init.ov.w.width = 320;
> btv->init.ov.w.height = 240;

The patch is good here too. Thanks.

Tested-by: Chris Clayton <chris2553@googlemail.com>



--
The more I see, the more I know. The more I know, the less I understand.
Changing Man - Paul Weller


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