* [PATCH] rcar-vin: fix null pointer dereference in rvin_group_get()
@ 2018-04-24 23:45 Niklas Söderlund
2018-04-25 7:18 ` Simon Horman
2018-04-25 7:25 ` Geert Uytterhoeven
0 siblings, 2 replies; 6+ messages in thread
From: Niklas Söderlund @ 2018-04-24 23:45 UTC (permalink / raw)
To: Laurent Pinchart, Hans Verkuil, linux-media
Cc: linux-renesas-soc, Niklas Söderlund
Store the group pointer before disassociating the VIN from the group.
Fixes: 3bb4c3bc85bf77a7 ("media: rcar-vin: add group allocator functions")
Reported-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
---
drivers/media/platform/rcar-vin/rcar-core.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/drivers/media/platform/rcar-vin/rcar-core.c b/drivers/media/platform/rcar-vin/rcar-core.c
index 7bc2774a11232362..d3072e166a1ca24f 100644
--- a/drivers/media/platform/rcar-vin/rcar-core.c
+++ b/drivers/media/platform/rcar-vin/rcar-core.c
@@ -338,19 +338,21 @@ static int rvin_group_get(struct rvin_dev *vin)
static void rvin_group_put(struct rvin_dev *vin)
{
- mutex_lock(&vin->group->lock);
+ struct rvin_group *group = vin->group;
+
+ mutex_lock(&group->lock);
vin->group = NULL;
vin->v4l2_dev.mdev = NULL;
- if (WARN_ON(vin->group->vin[vin->id] != vin))
+ if (WARN_ON(group->vin[vin->id] != vin))
goto out;
- vin->group->vin[vin->id] = NULL;
+ group->vin[vin->id] = NULL;
out:
- mutex_unlock(&vin->group->lock);
+ mutex_unlock(&group->lock);
- kref_put(&vin->group->refcount, rvin_group_release);
+ kref_put(&group->refcount, rvin_group_release);
}
/* -----------------------------------------------------------------------------
--
2.17.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] rcar-vin: fix null pointer dereference in rvin_group_get()
2018-04-24 23:45 [PATCH] rcar-vin: fix null pointer dereference in rvin_group_get() Niklas Söderlund
@ 2018-04-25 7:18 ` Simon Horman
2018-04-26 15:20 ` Niklas Söderlund
2018-04-25 7:25 ` Geert Uytterhoeven
1 sibling, 1 reply; 6+ messages in thread
From: Simon Horman @ 2018-04-25 7:18 UTC (permalink / raw)
To: Niklas Söderlund
Cc: Laurent Pinchart, Hans Verkuil, linux-media, linux-renesas-soc
On Wed, Apr 25, 2018 at 01:45:06AM +0200, Niklas Söderlund wrote:
> Store the group pointer before disassociating the VIN from the group.
>
> Fixes: 3bb4c3bc85bf77a7 ("media: rcar-vin: add group allocator functions")
> Reported-by: Colin Ian King <colin.king@canonical.com>
> Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
> ---
> drivers/media/platform/rcar-vin/rcar-core.c | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/media/platform/rcar-vin/rcar-core.c b/drivers/media/platform/rcar-vin/rcar-core.c
> index 7bc2774a11232362..d3072e166a1ca24f 100644
> --- a/drivers/media/platform/rcar-vin/rcar-core.c
> +++ b/drivers/media/platform/rcar-vin/rcar-core.c
> @@ -338,19 +338,21 @@ static int rvin_group_get(struct rvin_dev *vin)
>
> static void rvin_group_put(struct rvin_dev *vin)
> {
> - mutex_lock(&vin->group->lock);
> + struct rvin_group *group = vin->group;
> +
> + mutex_lock(&group->lock);
Hi Niklas, its not clear to me why moving the lock is safe.
Could you explain the locking scheme a little?
>
> vin->group = NULL;
> vin->v4l2_dev.mdev = NULL;
>
> - if (WARN_ON(vin->group->vin[vin->id] != vin))
> + if (WARN_ON(group->vin[vin->id] != vin))
> goto out;
>
> - vin->group->vin[vin->id] = NULL;
> + group->vin[vin->id] = NULL;
> out:
> - mutex_unlock(&vin->group->lock);
> + mutex_unlock(&group->lock);
>
> - kref_put(&vin->group->refcount, rvin_group_release);
> + kref_put(&group->refcount, rvin_group_release);
> }
>
> /* -----------------------------------------------------------------------------
> --
> 2.17.0
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] rcar-vin: fix null pointer dereference in rvin_group_get()
2018-04-24 23:45 [PATCH] rcar-vin: fix null pointer dereference in rvin_group_get() Niklas Söderlund
2018-04-25 7:18 ` Simon Horman
@ 2018-04-25 7:25 ` Geert Uytterhoeven
2018-04-26 15:21 ` Niklas Söderlund
1 sibling, 1 reply; 6+ messages in thread
From: Geert Uytterhoeven @ 2018-04-25 7:25 UTC (permalink / raw)
To: Niklas Söderlund
Cc: Laurent Pinchart, Hans Verkuil, Linux Media Mailing List, Linux-Renesas
On Wed, Apr 25, 2018 at 1:45 AM, Niklas Söderlund
<niklas.soderlund+renesas@ragnatech.se> wrote:
> Store the group pointer before disassociating the VIN from the group.
s/get/put/ in one-line summary?
> Fixes: 3bb4c3bc85bf77a7 ("media: rcar-vin: add group allocator functions")
> Reported-by: Colin Ian King <colin.king@canonical.com>
> Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
> ---
> drivers/media/platform/rcar-vin/rcar-core.c | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/media/platform/rcar-vin/rcar-core.c b/drivers/media/platform/rcar-vin/rcar-core.c
> index 7bc2774a11232362..d3072e166a1ca24f 100644
> --- a/drivers/media/platform/rcar-vin/rcar-core.c
> +++ b/drivers/media/platform/rcar-vin/rcar-core.c
> @@ -338,19 +338,21 @@ static int rvin_group_get(struct rvin_dev *vin)
>
> static void rvin_group_put(struct rvin_dev *vin)
> {
> - mutex_lock(&vin->group->lock);
> + struct rvin_group *group = vin->group;
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] rcar-vin: fix null pointer dereference in rvin_group_get()
2018-04-25 7:18 ` Simon Horman
@ 2018-04-26 15:20 ` Niklas Söderlund
2018-04-30 7:10 ` Simon Horman
0 siblings, 1 reply; 6+ messages in thread
From: Niklas Söderlund @ 2018-04-26 15:20 UTC (permalink / raw)
To: Simon Horman
Cc: Laurent Pinchart, Hans Verkuil, linux-media, linux-renesas-soc
Hi Simon,
Thanks for your feedback.
On 2018-04-25 09:18:51 +0200, Simon Horman wrote:
> On Wed, Apr 25, 2018 at 01:45:06AM +0200, Niklas Söderlund wrote:
> > Store the group pointer before disassociating the VIN from the group.
> >
> > Fixes: 3bb4c3bc85bf77a7 ("media: rcar-vin: add group allocator functions")
> > Reported-by: Colin Ian King <colin.king@canonical.com>
> > Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
> > ---
> > drivers/media/platform/rcar-vin/rcar-core.c | 12 +++++++-----
> > 1 file changed, 7 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/media/platform/rcar-vin/rcar-core.c b/drivers/media/platform/rcar-vin/rcar-core.c
> > index 7bc2774a11232362..d3072e166a1ca24f 100644
> > --- a/drivers/media/platform/rcar-vin/rcar-core.c
> > +++ b/drivers/media/platform/rcar-vin/rcar-core.c
> > @@ -338,19 +338,21 @@ static int rvin_group_get(struct rvin_dev *vin)
> >
> > static void rvin_group_put(struct rvin_dev *vin)
> > {
> > - mutex_lock(&vin->group->lock);
> > + struct rvin_group *group = vin->group;
> > +
> > + mutex_lock(&group->lock);
>
> Hi Niklas, its not clear to me why moving the lock is safe.
> Could you explain the locking scheme a little?
The lock here protects the members of the group struct and not any of
the members of the vin struct. The intent of the rvin_group_put()
function is:
1. Disassociate the vin struct from the group struct. This is done by
removing the pointer to the vin from the group->vin array and
removing the pointer from vin->group to the group struct. Here the
lock is needed to protect access to the group->vin array.
2. Decrease the refcount of the struct group and if we are the last one
out release the group.
The problem with the original code is that I first disassociate group
from the vin 'vin->group = NULL' but still use the pointer stored in the
vin struct when I try to disassociate the vin from the group
'vin->group->vin[vin->id]'.
AFIK can tell the locking here is fine, the problem was that I pulled
the rug from under my own feet in how I access the lock in order to not
having to declare a variable to store the pointer in ;-)
Do this explanation help put you at ease?
>
> >
> > vin->group = NULL;
> > vin->v4l2_dev.mdev = NULL;
> >
> > - if (WARN_ON(vin->group->vin[vin->id] != vin))
> > + if (WARN_ON(group->vin[vin->id] != vin))
> > goto out;
> >
> > - vin->group->vin[vin->id] = NULL;
> > + group->vin[vin->id] = NULL;
> > out:
> > - mutex_unlock(&vin->group->lock);
> > + mutex_unlock(&group->lock);
> >
> > - kref_put(&vin->group->refcount, rvin_group_release);
> > + kref_put(&group->refcount, rvin_group_release);
> > }
> >
> > /* -----------------------------------------------------------------------------
> > --
> > 2.17.0
> >
--
Regards,
Niklas Söderlund
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] rcar-vin: fix null pointer dereference in rvin_group_get()
2018-04-25 7:25 ` Geert Uytterhoeven
@ 2018-04-26 15:21 ` Niklas Söderlund
0 siblings, 0 replies; 6+ messages in thread
From: Niklas Söderlund @ 2018-04-26 15:21 UTC (permalink / raw)
To: Geert Uytterhoeven
Cc: Laurent Pinchart, Hans Verkuil, Linux Media Mailing List, Linux-Renesas
Hi Geert,
Thanks for your feedback.
On 2018-04-25 09:25:56 +0200, Geert Uytterhoeven wrote:
> On Wed, Apr 25, 2018 at 1:45 AM, Niklas Söderlund
> <niklas.soderlund+renesas@ragnatech.se> wrote:
> > Store the group pointer before disassociating the VIN from the group.
>
> s/get/put/ in one-line summary?
Yes, silly copy paste error, must have copied function name from the @@
context line and not from the diff itself. Thanks for noticing.
Will send a v2 after I have checked with Simon that the is happy with
the change itself.
>
> > Fixes: 3bb4c3bc85bf77a7 ("media: rcar-vin: add group allocator functions")
> > Reported-by: Colin Ian King <colin.king@canonical.com>
> > Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
> > ---
> > drivers/media/platform/rcar-vin/rcar-core.c | 12 +++++++-----
> > 1 file changed, 7 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/media/platform/rcar-vin/rcar-core.c b/drivers/media/platform/rcar-vin/rcar-core.c
> > index 7bc2774a11232362..d3072e166a1ca24f 100644
> > --- a/drivers/media/platform/rcar-vin/rcar-core.c
> > +++ b/drivers/media/platform/rcar-vin/rcar-core.c
> > @@ -338,19 +338,21 @@ static int rvin_group_get(struct rvin_dev *vin)
> >
> > static void rvin_group_put(struct rvin_dev *vin)
> > {
> > - mutex_lock(&vin->group->lock);
> > + struct rvin_group *group = vin->group;
>
> Gr{oetje,eeting}s,
>
> Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
> -- Linus Torvalds
--
Regards,
Niklas Söderlund
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] rcar-vin: fix null pointer dereference in rvin_group_get()
2018-04-26 15:20 ` Niklas Söderlund
@ 2018-04-30 7:10 ` Simon Horman
0 siblings, 0 replies; 6+ messages in thread
From: Simon Horman @ 2018-04-30 7:10 UTC (permalink / raw)
To: Niklas Söderlund
Cc: Laurent Pinchart, Hans Verkuil, linux-media, linux-renesas-soc
On Thu, Apr 26, 2018 at 05:20:05PM +0200, Niklas Söderlund wrote:
> Hi Simon,
>
> Thanks for your feedback.
>
> On 2018-04-25 09:18:51 +0200, Simon Horman wrote:
> > On Wed, Apr 25, 2018 at 01:45:06AM +0200, Niklas Söderlund wrote:
> > > Store the group pointer before disassociating the VIN from the group.
> > >
> > > Fixes: 3bb4c3bc85bf77a7 ("media: rcar-vin: add group allocator functions")
> > > Reported-by: Colin Ian King <colin.king@canonical.com>
> > > Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
> > > ---
> > > drivers/media/platform/rcar-vin/rcar-core.c | 12 +++++++-----
> > > 1 file changed, 7 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/drivers/media/platform/rcar-vin/rcar-core.c b/drivers/media/platform/rcar-vin/rcar-core.c
> > > index 7bc2774a11232362..d3072e166a1ca24f 100644
> > > --- a/drivers/media/platform/rcar-vin/rcar-core.c
> > > +++ b/drivers/media/platform/rcar-vin/rcar-core.c
> > > @@ -338,19 +338,21 @@ static int rvin_group_get(struct rvin_dev *vin)
> > >
> > > static void rvin_group_put(struct rvin_dev *vin)
> > > {
> > > - mutex_lock(&vin->group->lock);
> > > + struct rvin_group *group = vin->group;
> > > +
> > > + mutex_lock(&group->lock);
> >
> > Hi Niklas, its not clear to me why moving the lock is safe.
> > Could you explain the locking scheme a little?
>
> The lock here protects the members of the group struct and not any of
> the members of the vin struct. The intent of the rvin_group_put()
> function is:
>
> 1. Disassociate the vin struct from the group struct. This is done by
> removing the pointer to the vin from the group->vin array and
> removing the pointer from vin->group to the group struct. Here the
> lock is needed to protect access to the group->vin array.
>
> 2. Decrease the refcount of the struct group and if we are the last one
> out release the group.
>
> The problem with the original code is that I first disassociate group
> from the vin 'vin->group = NULL' but still use the pointer stored in the
> vin struct when I try to disassociate the vin from the group
> 'vin->group->vin[vin->id]'.
>
> AFIK can tell the locking here is fine, the problem was that I pulled
> the rug from under my own feet in how I access the lock in order to not
> having to declare a variable to store the pointer in ;-)
>
> Do this explanation help put you at ease?
Thanks, I am completely relaxed now :)
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
> > > vin->group = NULL;
> > > vin->v4l2_dev.mdev = NULL;
> > >
> > > - if (WARN_ON(vin->group->vin[vin->id] != vin))
> > > + if (WARN_ON(group->vin[vin->id] != vin))
> > > goto out;
> > >
> > > - vin->group->vin[vin->id] = NULL;
> > > + group->vin[vin->id] = NULL;
> > > out:
> > > - mutex_unlock(&vin->group->lock);
> > > + mutex_unlock(&group->lock);
> > >
> > > - kref_put(&vin->group->refcount, rvin_group_release);
> > > + kref_put(&group->refcount, rvin_group_release);
> > > }
> > >
> > > /* -----------------------------------------------------------------------------
> > > --
> > > 2.17.0
> > >
>
> --
> Regards,
> Niklas Söderlund
>
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2018-04-30 7:10 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2018-04-24 23:45 [PATCH] rcar-vin: fix null pointer dereference in rvin_group_get() Niklas Söderlund
2018-04-25 7:18 ` Simon Horman
2018-04-26 15:20 ` Niklas Söderlund
2018-04-30 7:10 ` Simon Horman
2018-04-25 7:25 ` Geert Uytterhoeven
2018-04-26 15:21 ` Niklas Söderlund
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