* [Patch V2] v4l2-core: fix use-after-free error
@ 2019-04-11 16:01 Sumit Gupta
2019-04-12 11:23 ` Hans Verkuil
0 siblings, 1 reply; 4+ messages in thread
From: Sumit Gupta @ 2019-04-11 16:01 UTC (permalink / raw)
To: mchehab, hverkuil-cisco, sakari.ailus, paul.kocialkowski, tfiga,
keiichiw, sumitg, bbasu
Cc: linux-media, linux-kernel
From: sumitg <sumitg@nvidia.com>
Fixing use-after-free within __v4l2_ctrl_handler_setup().
Memory is being freed with kfree(new_ref) for duplicate
control reference entry but cluster is still referring
to the duplicate entry. Change done to update ctrl->cluster
only when new control reference is added. Also, checking if
ctrl->ncontrols is non-zero before accessing controls from
cluster pointer to avoid illegal access when cluster has
zero controls.
==================================================================
BUG: KASAN: use-after-free in __v4l2_ctrl_handler_setup+0x388/0x428
Read of size 8 at addr ffffffc324e78618 by task systemd-udevd/312
Allocated by task 312:
Freed by task 312:
The buggy address belongs to the object at ffffffc324e78600
which belongs to the cache kmalloc-64 of size 64
The buggy address is located 24 bytes inside of
64-byte region [ffffffc324e78600, ffffffc324e78640)
The buggy address belongs to the page:
page:ffffffbf0c939e00 count:1 mapcount:0 mapping:
(null) index:0xffffffc324e78f80
flags: 0x4000000000000100(slab)
raw: 4000000000000100 0000000000000000 ffffffc324e78f80 000000018020001a
raw: 0000000000000000 0000000100000001 ffffffc37040fb80 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffffffc324e78500: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffffffc324e78580: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>ffffffc324e78600: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
^
ffffffc324e78680: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
ffffffc324e78700: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
==================================================================
Suggested-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Sumit Gupta <sumitg@nvidia.com>
---
v2:
* update ctrl->cluster only when new control reference is added.
* check ctrl->ncontrols to avoid illegal access when cluster has zero controls.
drivers/media/v4l2-core/v4l2-ctrls.c | 53 +++++++++++++++++++-----------------
1 file changed, 28 insertions(+), 25 deletions(-)
diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
index 5e3806f..3d0a952 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls.c
@@ -2154,15 +2154,6 @@ static int handler_new_ref(struct v4l2_ctrl_handler *hdl,
if (size_extra_req)
new_ref->p_req.p = &new_ref[1];
- if (ctrl->handler == hdl) {
- /* By default each control starts in a cluster of its own.
- new_ref->ctrl is basically a cluster array with one
- element, so that's perfect to use as the cluster pointer.
- But only do this for the handler that owns the control. */
- ctrl->cluster = &new_ref->ctrl;
- ctrl->ncontrols = 1;
- }
-
INIT_LIST_HEAD(&new_ref->node);
mutex_lock(hdl->lock);
@@ -2195,6 +2186,15 @@ static int handler_new_ref(struct v4l2_ctrl_handler *hdl,
hdl->buckets[bucket] = new_ref;
if (ctrl_ref)
*ctrl_ref = new_ref;
+ if (ctrl->handler == hdl) {
+ /* By default each control starts in a cluster of its own.
+ * new_ref->ctrl is basically a cluster array with one
+ * element, so that's perfect to use as the cluster pointer.
+ * But only do this for the handler that owns the control.
+ */
+ ctrl->cluster = &new_ref->ctrl;
+ ctrl->ncontrols = 1;
+ }
unlock:
mutex_unlock(hdl->lock);
@@ -2725,25 +2725,28 @@ int __v4l2_ctrl_handler_setup(struct v4l2_ctrl_handler *hdl)
ctrl->done = false;
list_for_each_entry(ctrl, &hdl->ctrls, node) {
- struct v4l2_ctrl *master = ctrl->cluster[0];
- int i;
-
- /* Skip if this control was already handled by a cluster. */
- /* Skip button controls and read-only controls. */
- if (ctrl->done || ctrl->type == V4L2_CTRL_TYPE_BUTTON ||
- (ctrl->flags & V4L2_CTRL_FLAG_READ_ONLY))
- continue;
+ if (ctrl->ncontrols) {
+ struct v4l2_ctrl *master = ctrl->cluster[0];
+ int i;
+
+ /* Skip if this control was already handled by a */
+ /* cluster. Skip button controls and read-only */
+ /* controls. */
+ if (ctrl->done || ctrl->type == V4L2_CTRL_TYPE_BUTTON ||
+ (ctrl->flags & V4L2_CTRL_FLAG_READ_ONLY))
+ continue;
- for (i = 0; i < master->ncontrols; i++) {
- if (master->cluster[i]) {
- cur_to_new(master->cluster[i]);
- master->cluster[i]->is_new = 1;
- master->cluster[i]->done = true;
+ for (i = 0; i < master->ncontrols; i++) {
+ if (master->cluster[i]) {
+ cur_to_new(master->cluster[i]);
+ master->cluster[i]->is_new = 1;
+ master->cluster[i]->done = true;
+ }
}
+ ret = call_op(master, s_ctrl);
+ if (ret)
+ break;
}
- ret = call_op(master, s_ctrl);
- if (ret)
- break;
}
return ret;
--
2.7.4
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [Patch V2] v4l2-core: fix use-after-free error
2019-04-11 16:01 [Patch V2] v4l2-core: fix use-after-free error Sumit Gupta
@ 2019-04-12 11:23 ` Hans Verkuil
2019-04-12 13:47 ` Sumit Gupta
0 siblings, 1 reply; 4+ messages in thread
From: Hans Verkuil @ 2019-04-12 11:23 UTC (permalink / raw)
To: Sumit Gupta, mchehab, sakari.ailus, paul.kocialkowski, tfiga,
keiichiw, bbasu
Cc: linux-media, linux-kernel
On 4/11/19 6:01 PM, Sumit Gupta wrote:
> From: sumitg <sumitg@nvidia.com>
>
> Fixing use-after-free within __v4l2_ctrl_handler_setup().
> Memory is being freed with kfree(new_ref) for duplicate
> control reference entry but cluster is still referring
> to the duplicate entry. Change done to update ctrl->cluster
> only when new control reference is added. Also, checking if
> ctrl->ncontrols is non-zero before accessing controls from
> cluster pointer to avoid illegal access when cluster has
> zero controls.
>
> ==================================================================
> BUG: KASAN: use-after-free in __v4l2_ctrl_handler_setup+0x388/0x428
> Read of size 8 at addr ffffffc324e78618 by task systemd-udevd/312
>
> Allocated by task 312:
>
> Freed by task 312:
>
> The buggy address belongs to the object at ffffffc324e78600
> which belongs to the cache kmalloc-64 of size 64
> The buggy address is located 24 bytes inside of
> 64-byte region [ffffffc324e78600, ffffffc324e78640)
> The buggy address belongs to the page:
> page:ffffffbf0c939e00 count:1 mapcount:0 mapping:
> (null) index:0xffffffc324e78f80
> flags: 0x4000000000000100(slab)
> raw: 4000000000000100 0000000000000000 ffffffc324e78f80 000000018020001a
> raw: 0000000000000000 0000000100000001 ffffffc37040fb80 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
> ffffffc324e78500: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
> ffffffc324e78580: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
> >ffffffc324e78600: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
> ^
> ffffffc324e78680: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
> ffffffc324e78700: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
> ==================================================================
>
> Suggested-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
> Signed-off-by: Sumit Gupta <sumitg@nvidia.com>
> ---
> v2:
> * update ctrl->cluster only when new control reference is added.
> * check ctrl->ncontrols to avoid illegal access when cluster has zero controls.
>
> drivers/media/v4l2-core/v4l2-ctrls.c | 53 +++++++++++++++++++-----------------
> 1 file changed, 28 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
> index 5e3806f..3d0a952 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
> @@ -2154,15 +2154,6 @@ static int handler_new_ref(struct v4l2_ctrl_handler *hdl,
> if (size_extra_req)
> new_ref->p_req.p = &new_ref[1];
>
> - if (ctrl->handler == hdl) {
> - /* By default each control starts in a cluster of its own.
> - new_ref->ctrl is basically a cluster array with one
> - element, so that's perfect to use as the cluster pointer.
> - But only do this for the handler that owns the control. */
> - ctrl->cluster = &new_ref->ctrl;
> - ctrl->ncontrols = 1;
> - }
> -
> INIT_LIST_HEAD(&new_ref->node);
>
> mutex_lock(hdl->lock);
> @@ -2195,6 +2186,15 @@ static int handler_new_ref(struct v4l2_ctrl_handler *hdl,
> hdl->buckets[bucket] = new_ref;
> if (ctrl_ref)
> *ctrl_ref = new_ref;
> + if (ctrl->handler == hdl) {
> + /* By default each control starts in a cluster of its own.
> + * new_ref->ctrl is basically a cluster array with one
> + * element, so that's perfect to use as the cluster pointer.
> + * But only do this for the handler that owns the control.
> + */
> + ctrl->cluster = &new_ref->ctrl;
> + ctrl->ncontrols = 1;
> + }
>
> unlock:
> mutex_unlock(hdl->lock);
This looks good.
> @@ -2725,25 +2725,28 @@ int __v4l2_ctrl_handler_setup(struct v4l2_ctrl_handler *hdl)
> ctrl->done = false;
>
> list_for_each_entry(ctrl, &hdl->ctrls, node) {
> - struct v4l2_ctrl *master = ctrl->cluster[0];
> - int i;
> -
> - /* Skip if this control was already handled by a cluster. */
> - /* Skip button controls and read-only controls. */
> - if (ctrl->done || ctrl->type == V4L2_CTRL_TYPE_BUTTON ||
> - (ctrl->flags & V4L2_CTRL_FLAG_READ_ONLY))
> - continue;
> + if (ctrl->ncontrols) {
> + struct v4l2_ctrl *master = ctrl->cluster[0];
> + int i;
> +
> + /* Skip if this control was already handled by a */
> + /* cluster. Skip button controls and read-only */
> + /* controls. */
> + if (ctrl->done || ctrl->type == V4L2_CTRL_TYPE_BUTTON ||
> + (ctrl->flags & V4L2_CTRL_FLAG_READ_ONLY))
> + continue;
>
> - for (i = 0; i < master->ncontrols; i++) {
> - if (master->cluster[i]) {
> - cur_to_new(master->cluster[i]);
> - master->cluster[i]->is_new = 1;
> - master->cluster[i]->done = true;
> + for (i = 0; i < master->ncontrols; i++) {
> + if (master->cluster[i]) {
> + cur_to_new(master->cluster[i]);
> + master->cluster[i]->is_new = 1;
> + master->cluster[i]->done = true;
> + }
> }
> + ret = call_op(master, s_ctrl);
> + if (ret)
> + break;
> }
> - ret = call_op(master, s_ctrl);
> - if (ret)
> - break;
> }
>
> return ret;
>
These changes shouldn't be needed: when you get here all controls are
guaranteed to have a non-0 ncontrols value.
If it is possible to encounter a control where ncontrols == 0, then
that's a bug elsewhere. But as far as I can tell that isn't the case.
Regards,
Hans
^ permalink raw reply [flat|nested] 4+ messages in thread
* RE: [Patch V2] v4l2-core: fix use-after-free error
2019-04-12 11:23 ` Hans Verkuil
@ 2019-04-12 13:47 ` Sumit Gupta
2019-04-12 13:55 ` Hans Verkuil
0 siblings, 1 reply; 4+ messages in thread
From: Sumit Gupta @ 2019-04-12 13:47 UTC (permalink / raw)
To: Hans Verkuil, mchehab, sakari.ailus, paul.kocialkowski, tfiga,
keiichiw, Bibek Basu
Cc: linux-media, linux-kernel
On 4/11/19 6:01 PM, Sumit Gupta wrote:
> From: sumitg <sumitg@nvidia.com>
>
> Fixing use-after-free within __v4l2_ctrl_handler_setup().
> Memory is being freed with kfree(new_ref) for duplicate control
> reference entry but cluster is still referring to the duplicate entry.
> Change done to update ctrl->cluster only when new control reference is
> added. Also, checking if
> ctrl->ncontrols is non-zero before accessing controls from
> cluster pointer to avoid illegal access when cluster has zero
> controls.
>
> ==================================================================
> BUG: KASAN: use-after-free in __v4l2_ctrl_handler_setup+0x388/0x428
> Read of size 8 at addr ffffffc324e78618 by task systemd-udevd/312
>
> Allocated by task 312:
>
> Freed by task 312:
>
> The buggy address belongs to the object at ffffffc324e78600
> which belongs to the cache kmalloc-64 of size 64 The buggy address
> is located 24 bytes inside of
> 64-byte region [ffffffc324e78600, ffffffc324e78640) The buggy
> address belongs to the page:
> page:ffffffbf0c939e00 count:1 mapcount:0 mapping:
> (null) index:0xffffffc324e78f80
> flags: 0x4000000000000100(slab)
> raw: 4000000000000100 0000000000000000 ffffffc324e78f80
> 000000018020001a
> raw: 0000000000000000 0000000100000001 ffffffc37040fb80
> 0000000000000000 page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
> ffffffc324e78500: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
> ffffffc324e78580: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
> >ffffffc324e78600: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
> ^
> ffffffc324e78680: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
> ffffffc324e78700: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
> ==================================================================
>
> Suggested-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
> Signed-off-by: Sumit Gupta <sumitg@nvidia.com>
> ---
> v2:
> * update ctrl->cluster only when new control reference is added.
> * check ctrl->ncontrols to avoid illegal access when cluster has zero controls.
>
> drivers/media/v4l2-core/v4l2-ctrls.c | 53
> +++++++++++++++++++-----------------
> 1 file changed, 28 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c
> b/drivers/media/v4l2-core/v4l2-ctrls.c
> index 5e3806f..3d0a952 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
> @@ -2154,15 +2154,6 @@ static int handler_new_ref(struct v4l2_ctrl_handler *hdl,
> if (size_extra_req)
> new_ref->p_req.p = &new_ref[1];
>
> - if (ctrl->handler == hdl) {
> - /* By default each control starts in a cluster of its own.
> - new_ref->ctrl is basically a cluster array with one
> - element, so that's perfect to use as the cluster pointer.
> - But only do this for the handler that owns the control. */
> - ctrl->cluster = &new_ref->ctrl;
> - ctrl->ncontrols = 1;
> - }
> -
> INIT_LIST_HEAD(&new_ref->node);
>
> mutex_lock(hdl->lock);
> @@ -2195,6 +2186,15 @@ static int handler_new_ref(struct v4l2_ctrl_handler *hdl,
> hdl->buckets[bucket] = new_ref;
> if (ctrl_ref)
> *ctrl_ref = new_ref;
> + if (ctrl->handler == hdl) {
> + /* By default each control starts in a cluster of its own.
> + * new_ref->ctrl is basically a cluster array with one
> + * element, so that's perfect to use as the cluster pointer.
> + * But only do this for the handler that owns the control.
> + */
> + ctrl->cluster = &new_ref->ctrl;
> + ctrl->ncontrols = 1;
> + }
>
> unlock:
> mutex_unlock(hdl->lock);
This looks good.
> @@ -2725,25 +2725,28 @@ int __v4l2_ctrl_handler_setup(struct v4l2_ctrl_handler *hdl)
> ctrl->done = false;
>
> list_for_each_entry(ctrl, &hdl->ctrls, node) {
> - struct v4l2_ctrl *master = ctrl->cluster[0];
> - int i;
> -
> - /* Skip if this control was already handled by a cluster. */
> - /* Skip button controls and read-only controls. */
> - if (ctrl->done || ctrl->type == V4L2_CTRL_TYPE_BUTTON ||
> - (ctrl->flags & V4L2_CTRL_FLAG_READ_ONLY))
> - continue;
> + if (ctrl->ncontrols) {
> + struct v4l2_ctrl *master = ctrl->cluster[0];
> + int i;
> +
> + /* Skip if this control was already handled by a */
> + /* cluster. Skip button controls and read-only */
> + /* controls. */
> + if (ctrl->done || ctrl->type == V4L2_CTRL_TYPE_BUTTON ||
> + (ctrl->flags & V4L2_CTRL_FLAG_READ_ONLY))
> + continue;
>
> - for (i = 0; i < master->ncontrols; i++) {
> - if (master->cluster[i]) {
> - cur_to_new(master->cluster[i]);
> - master->cluster[i]->is_new = 1;
> - master->cluster[i]->done = true;
> + for (i = 0; i < master->ncontrols; i++) {
> + if (master->cluster[i]) {
> + cur_to_new(master->cluster[i]);
> + master->cluster[i]->is_new = 1;
> + master->cluster[i]->done = true;
> + }
> }
> + ret = call_op(master, s_ctrl);
> + if (ret)
> + break;
> }
> - ret = call_op(master, s_ctrl);
> - if (ret)
> - break;
> }
>
> return ret;
>
These changes shouldn't be needed: when you get here all controls are guaranteed to have a non-0 ncontrols value.
If it is possible to encounter a control where ncontrols == 0, then that's a bug elsewhere. But as far as I can tell that isn't the case.
Regards,
Hans
Yes, I am getting a control where ncontrols is zero as printed below.
It can be another bug as you said. I think, adding check here will be
helpful to not crash in such cases. Please share if you think otherwise,
then will remove the check.
int __v4l2_ctrl_handler_setup(struct v4l2_ctrl_handler *hdl)
ctrl->done = false;
list_for_each_entry(ctrl, &hdl->ctrls, node) {
+ if (ctrl->ncontrols == 0)
+ pr_crit("<func:%s><ctrl->name:%s><ctrl->ncontrols:%d>\n",
+ __func__, ctrl->name, ctrl->ncontrols);
Log:
[ 8.354464] <func:__v4l2_ctrl_handler_setup><ctrl->name:Group Hold><ctrl->ncontrols:0>
Regards,
Sumit Gupta
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [Patch V2] v4l2-core: fix use-after-free error
2019-04-12 13:47 ` Sumit Gupta
@ 2019-04-12 13:55 ` Hans Verkuil
0 siblings, 0 replies; 4+ messages in thread
From: Hans Verkuil @ 2019-04-12 13:55 UTC (permalink / raw)
To: Sumit Gupta, mchehab, sakari.ailus, paul.kocialkowski, tfiga,
keiichiw, Bibek Basu
Cc: linux-media, linux-kernel
On 4/12/19 3:47 PM, Sumit Gupta wrote:
>
> On 4/11/19 6:01 PM, Sumit Gupta wrote:
>> From: sumitg <sumitg@nvidia.com>
>>
>> Fixing use-after-free within __v4l2_ctrl_handler_setup().
>> Memory is being freed with kfree(new_ref) for duplicate control
>> reference entry but cluster is still referring to the duplicate entry.
>> Change done to update ctrl->cluster only when new control reference is
>> added. Also, checking if
>> ctrl->ncontrols is non-zero before accessing controls from
>> cluster pointer to avoid illegal access when cluster has zero
>> controls.
>>
>> ==================================================================
>> BUG: KASAN: use-after-free in __v4l2_ctrl_handler_setup+0x388/0x428
>> Read of size 8 at addr ffffffc324e78618 by task systemd-udevd/312
>>
>> Allocated by task 312:
>>
>> Freed by task 312:
>>
>> The buggy address belongs to the object at ffffffc324e78600
>> which belongs to the cache kmalloc-64 of size 64 The buggy address
>> is located 24 bytes inside of
>> 64-byte region [ffffffc324e78600, ffffffc324e78640) The buggy
>> address belongs to the page:
>> page:ffffffbf0c939e00 count:1 mapcount:0 mapping:
>> (null) index:0xffffffc324e78f80
>> flags: 0x4000000000000100(slab)
>> raw: 4000000000000100 0000000000000000 ffffffc324e78f80
>> 000000018020001a
>> raw: 0000000000000000 0000000100000001 ffffffc37040fb80
>> 0000000000000000 page dumped because: kasan: bad access detected
>>
>> Memory state around the buggy address:
>> ffffffc324e78500: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>> ffffffc324e78580: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>> >ffffffc324e78600: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>> ^
>> ffffffc324e78680: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
>> ffffffc324e78700: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
>> ==================================================================
>>
>> Suggested-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
>> Signed-off-by: Sumit Gupta <sumitg@nvidia.com>
>> ---
>> v2:
>> * update ctrl->cluster only when new control reference is added.
>> * check ctrl->ncontrols to avoid illegal access when cluster has zero controls.
>>
>> drivers/media/v4l2-core/v4l2-ctrls.c | 53
>> +++++++++++++++++++-----------------
>> 1 file changed, 28 insertions(+), 25 deletions(-)
>>
>> diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c
>> b/drivers/media/v4l2-core/v4l2-ctrls.c
>> index 5e3806f..3d0a952 100644
>> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
>> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
>> @@ -2154,15 +2154,6 @@ static int handler_new_ref(struct v4l2_ctrl_handler *hdl,
>> if (size_extra_req)
>> new_ref->p_req.p = &new_ref[1];
>>
>> - if (ctrl->handler == hdl) {
>> - /* By default each control starts in a cluster of its own.
>> - new_ref->ctrl is basically a cluster array with one
>> - element, so that's perfect to use as the cluster pointer.
>> - But only do this for the handler that owns the control. */
>> - ctrl->cluster = &new_ref->ctrl;
>> - ctrl->ncontrols = 1;
>> - }
>> -
>> INIT_LIST_HEAD(&new_ref->node);
>>
>> mutex_lock(hdl->lock);
>> @@ -2195,6 +2186,15 @@ static int handler_new_ref(struct v4l2_ctrl_handler *hdl,
>> hdl->buckets[bucket] = new_ref;
>> if (ctrl_ref)
>> *ctrl_ref = new_ref;
>> + if (ctrl->handler == hdl) {
>> + /* By default each control starts in a cluster of its own.
>> + * new_ref->ctrl is basically a cluster array with one
>> + * element, so that's perfect to use as the cluster pointer.
>> + * But only do this for the handler that owns the control.
>> + */
>> + ctrl->cluster = &new_ref->ctrl;
>> + ctrl->ncontrols = 1;
>> + }
>>
>> unlock:
>> mutex_unlock(hdl->lock);
>
> This looks good.
>
>> @@ -2725,25 +2725,28 @@ int __v4l2_ctrl_handler_setup(struct v4l2_ctrl_handler *hdl)
>> ctrl->done = false;
>>
>> list_for_each_entry(ctrl, &hdl->ctrls, node) {
>> - struct v4l2_ctrl *master = ctrl->cluster[0];
>> - int i;
>> -
>> - /* Skip if this control was already handled by a cluster. */
>> - /* Skip button controls and read-only controls. */
>> - if (ctrl->done || ctrl->type == V4L2_CTRL_TYPE_BUTTON ||
>> - (ctrl->flags & V4L2_CTRL_FLAG_READ_ONLY))
>> - continue;
>> + if (ctrl->ncontrols) {
>> + struct v4l2_ctrl *master = ctrl->cluster[0];
>> + int i;
>> +
>> + /* Skip if this control was already handled by a */
>> + /* cluster. Skip button controls and read-only */
>> + /* controls. */
>> + if (ctrl->done || ctrl->type == V4L2_CTRL_TYPE_BUTTON ||
>> + (ctrl->flags & V4L2_CTRL_FLAG_READ_ONLY))
>> + continue;
>>
>> - for (i = 0; i < master->ncontrols; i++) {
>> - if (master->cluster[i]) {
>> - cur_to_new(master->cluster[i]);
>> - master->cluster[i]->is_new = 1;
>> - master->cluster[i]->done = true;
>> + for (i = 0; i < master->ncontrols; i++) {
>> + if (master->cluster[i]) {
>> + cur_to_new(master->cluster[i]);
>> + master->cluster[i]->is_new = 1;
>> + master->cluster[i]->done = true;
>> + }
>> }
>> + ret = call_op(master, s_ctrl);
>> + if (ret)
>> + break;
>> }
>> - ret = call_op(master, s_ctrl);
>> - if (ret)
>> - break;
>> }
>>
>> return ret;
>>
>
> These changes shouldn't be needed: when you get here all controls are guaranteed to have a non-0 ncontrols value.
>
> If it is possible to encounter a control where ncontrols == 0, then that's a bug elsewhere. But as far as I can tell that isn't the case.
>
> Regards,
>
> Hans
>
> Yes, I am getting a control where ncontrols is zero as printed below.
> It can be another bug as you said. I think, adding check here will be
> helpful to not crash in such cases. Please share if you think otherwise,
> then will remove the check.
>
> int __v4l2_ctrl_handler_setup(struct v4l2_ctrl_handler *hdl)
> ctrl->done = false;
>
> list_for_each_entry(ctrl, &hdl->ctrls, node) {
> + if (ctrl->ncontrols == 0)
> + pr_crit("<func:%s><ctrl->name:%s><ctrl->ncontrols:%d>\n",
> + __func__, ctrl->name, ctrl->ncontrols);
>
> Log:
> [ 8.354464] <func:__v4l2_ctrl_handler_setup><ctrl->name:Group Hold><ctrl->ncontrols:0>
Something went wrong if you get this.
This should never happen. Dig a bit deeper to find out how you get into this situation.
You did check hdl->error before calling v4l2_ctrl_handler_setup? Although even if an error
occurred when adding controls, this should still not happen.
Regards,
Hans
>
>
> Regards,
> Sumit Gupta
>
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2019-04-12 13:55 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-04-11 16:01 [Patch V2] v4l2-core: fix use-after-free error Sumit Gupta
2019-04-12 11:23 ` Hans Verkuil
2019-04-12 13:47 ` Sumit Gupta
2019-04-12 13:55 ` Hans Verkuil
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