The list iterator will point to a bogus position containing HEAD if
the list is empty or the element is not found in list. This case
should be checked before any use of the iterator, otherwise it will
lead to a invalid memory access. The missing check here is before
"pin = iterm->id;", just add check here to fix the security bug.
In addition, the list iterator value will *always* be set and non-NULL
by list_for_each_entry(), so it is incorrect to assume that the iterator
value will be NULL if the element is not found in list, considering
the (mis)use here: "if (iterm == NULL".
Use a new value 'it' as the list iterator, while use the old value
'iterm' as a dedicated pointer to point to the found element, which
1. can fix this bug, due to 'iterm' is NULL only if it's not found.
2. do not need to change all the uses of 'iterm' after the loop.
3. can also limit the scope of the list iterator 'it' *only inside*
the traversal loop by simply declaring 'it' inside the loop in the
future, as usage of the iterator outside of the list_for_each_entry
is considered harmful. https://lkml.org/lkml/2022/2/17/1032
Fixes: d5e90b7a6cd1c ("[media] uvcvideo: Move to video_ioctl2")
Signed-off-by: Xiaomeng Tong <[email protected]>
---
drivers/media/usb/uvc/uvc_v4l2.c | 20 +++++++++++++-------
1 file changed, 13 insertions(+), 7 deletions(-)
diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
index 711556d13d03..e7cdc01ad277 100644
--- a/drivers/media/usb/uvc/uvc_v4l2.c
+++ b/drivers/media/usb/uvc/uvc_v4l2.c
@@ -871,6 +871,7 @@ static int uvc_ioctl_enum_input(struct file *file, void *fh,
struct uvc_video_chain *chain = handle->chain;
const struct uvc_entity *selector = chain->selector;
struct uvc_entity *iterm = NULL;
+ struct uvc_entity *it;
u32 index = input->index;
int pin = 0;
@@ -878,22 +879,27 @@ static int uvc_ioctl_enum_input(struct file *file, void *fh,
(chain->dev->quirks & UVC_QUIRK_IGNORE_SELECTOR_UNIT)) {
if (index != 0)
return -EINVAL;
- list_for_each_entry(iterm, &chain->entities, chain) {
- if (UVC_ENTITY_IS_ITERM(iterm))
+ list_for_each_entry(it, &chain->entities, chain) {
+ if (UVC_ENTITY_IS_ITERM(it)) {
+ iterm = it;
break;
+ }
}
- pin = iterm->id;
+ if (iterm)
+ pin = iterm->id;
} else if (index < selector->bNrInPins) {
pin = selector->baSourceID[index];
- list_for_each_entry(iterm, &chain->entities, chain) {
- if (!UVC_ENTITY_IS_ITERM(iterm))
+ list_for_each_entry(it, &chain->entities, chain) {
+ if (!UVC_ENTITY_IS_ITERM(it))
continue;
- if (iterm->id == pin)
+ if (it->id == pin) {
+ iterm = it;
break;
+ }
}
}
- if (iterm == NULL || iterm->id != pin)
+ if (iterm == NULL)
return -EINVAL;
memset(input, 0, sizeof(*input));
--
2.17.1
On Tue, Mar 22, 2022 at 01:40:07PM +0100, Ricardo Ribalda wrote:
> Hi Xiaomeng
>
> Thanks for the patch. Maybe it would be better to just make a function
> to find the ITERM entity with a given id?
We already have a uvc_entity_by_id() which could be used for that, but
only for the second loop iteration. The first one finds any input
terminal. Also, the second loop restricts the search to a chain, while
uvc_entity_by_id() it global to the device. I think the proposed patch
is fine.
> On Mon, 21 Mar 2022 at 16:33, Xiaomeng Tong wrote:
> >
> > The list iterator will point to a bogus position containing HEAD if
> > the list is empty or the element is not found in list. This case
> > should be checked before any use of the iterator, otherwise it will
> > lead to a invalid memory access. The missing check here is before
> > "pin = iterm->id;", just add check here to fix the security bug.
> >
> > In addition, the list iterator value will *always* be set and non-NULL
> > by list_for_each_entry(), so it is incorrect to assume that the iterator
> > value will be NULL if the element is not found in list, considering
> > the (mis)use here: "if (iterm == NULL".
> >
> > Use a new value 'it' as the list iterator, while use the old value
> > 'iterm' as a dedicated pointer to point to the found element, which
> > 1. can fix this bug, due to 'iterm' is NULL only if it's not found.
> > 2. do not need to change all the uses of 'iterm' after the loop.
> > 3. can also limit the scope of the list iterator 'it' *only inside*
> > the traversal loop by simply declaring 'it' inside the loop in the
> > future, as usage of the iterator outside of the list_for_each_entry
> > is considered harmful. https://lkml.org/lkml/2022/2/17/1032
Looking forward to that :-)
> > Fixes: d5e90b7a6cd1c ("[media] uvcvideo: Move to video_ioctl2")
> > Signed-off-by: Xiaomeng Tong <[email protected]>
> > ---
> > drivers/media/usb/uvc/uvc_v4l2.c | 20 +++++++++++++-------
> > 1 file changed, 13 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
> > index 711556d13d03..e7cdc01ad277 100644
> > --- a/drivers/media/usb/uvc/uvc_v4l2.c
> > +++ b/drivers/media/usb/uvc/uvc_v4l2.c
> > @@ -871,6 +871,7 @@ static int uvc_ioctl_enum_input(struct file *file, void *fh,
> > struct uvc_video_chain *chain = handle->chain;
> > const struct uvc_entity *selector = chain->selector;
> > struct uvc_entity *iterm = NULL;
> > + struct uvc_entity *it;
> > u32 index = input->index;
> > int pin = 0;
> >
> > @@ -878,22 +879,27 @@ static int uvc_ioctl_enum_input(struct file *file, void *fh,
> > (chain->dev->quirks & UVC_QUIRK_IGNORE_SELECTOR_UNIT)) {
> > if (index != 0)
> > return -EINVAL;
> > - list_for_each_entry(iterm, &chain->entities, chain) {
> > - if (UVC_ENTITY_IS_ITERM(iterm))
> > + list_for_each_entry(it, &chain->entities, chain) {
> > + if (UVC_ENTITY_IS_ITERM(it)) {
> > + iterm = it;
> > break;
> > + }
> > }
> > - pin = iterm->id;
> > + if (iterm)
> > + pin = iterm->id;
You can drop this, pin is not used anymore in the rest of the function.
> > } else if (index < selector->bNrInPins) {
> > pin = selector->baSourceID[index];
> > - list_for_each_entry(iterm, &chain->entities, chain) {
> > - if (!UVC_ENTITY_IS_ITERM(iterm))
> > + list_for_each_entry(it, &chain->entities, chain) {
> > + if (!UVC_ENTITY_IS_ITERM(it))
> > continue;
> > - if (iterm->id == pin)
> > + if (it->id == pin) {
And here you could use
if (it->id == selector->baSourceID[index]) {
and drop the local pin variable.
If you're fine with those small changes I can handle them when applying
the patch to my tree.
Reviewed-by: Laurent Pinchart <[email protected]>
> > + iterm = it;
> > break;
> > + }
> > }
> > }
> >
> > - if (iterm == NULL || iterm->id != pin)
> > + if (iterm == NULL)
> > return -EINVAL;
> >
> > memset(input, 0, sizeof(*input));
--
Regards,
Laurent Pinchart
Hi Xiaomeng
Thanks for the patch. Maybe it would be better to just make a function
to find the ITERM entity with a given id?
Regards!
On Mon, 21 Mar 2022 at 16:33, Xiaomeng Tong <[email protected]> wrote:
>
> The list iterator will point to a bogus position containing HEAD if
> the list is empty or the element is not found in list. This case
> should be checked before any use of the iterator, otherwise it will
> lead to a invalid memory access. The missing check here is before
> "pin = iterm->id;", just add check here to fix the security bug.
>
> In addition, the list iterator value will *always* be set and non-NULL
> by list_for_each_entry(), so it is incorrect to assume that the iterator
> value will be NULL if the element is not found in list, considering
> the (mis)use here: "if (iterm == NULL".
>
> Use a new value 'it' as the list iterator, while use the old value
> 'iterm' as a dedicated pointer to point to the found element, which
> 1. can fix this bug, due to 'iterm' is NULL only if it's not found.
> 2. do not need to change all the uses of 'iterm' after the loop.
> 3. can also limit the scope of the list iterator 'it' *only inside*
> the traversal loop by simply declaring 'it' inside the loop in the
> future, as usage of the iterator outside of the list_for_each_entry
> is considered harmful. https://lkml.org/lkml/2022/2/17/1032
>
> Fixes: d5e90b7a6cd1c ("[media] uvcvideo: Move to video_ioctl2")
> Signed-off-by: Xiaomeng Tong <[email protected]>
> ---
> drivers/media/usb/uvc/uvc_v4l2.c | 20 +++++++++++++-------
> 1 file changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
> index 711556d13d03..e7cdc01ad277 100644
> --- a/drivers/media/usb/uvc/uvc_v4l2.c
> +++ b/drivers/media/usb/uvc/uvc_v4l2.c
> @@ -871,6 +871,7 @@ static int uvc_ioctl_enum_input(struct file *file, void *fh,
> struct uvc_video_chain *chain = handle->chain;
> const struct uvc_entity *selector = chain->selector;
> struct uvc_entity *iterm = NULL;
> + struct uvc_entity *it;
> u32 index = input->index;
> int pin = 0;
>
> @@ -878,22 +879,27 @@ static int uvc_ioctl_enum_input(struct file *file, void *fh,
> (chain->dev->quirks & UVC_QUIRK_IGNORE_SELECTOR_UNIT)) {
> if (index != 0)
> return -EINVAL;
> - list_for_each_entry(iterm, &chain->entities, chain) {
> - if (UVC_ENTITY_IS_ITERM(iterm))
> + list_for_each_entry(it, &chain->entities, chain) {
> + if (UVC_ENTITY_IS_ITERM(it)) {
> + iterm = it;
> break;
> + }
> }
> - pin = iterm->id;
> + if (iterm)
> + pin = iterm->id;
> } else if (index < selector->bNrInPins) {
> pin = selector->baSourceID[index];
> - list_for_each_entry(iterm, &chain->entities, chain) {
> - if (!UVC_ENTITY_IS_ITERM(iterm))
> + list_for_each_entry(it, &chain->entities, chain) {
> + if (!UVC_ENTITY_IS_ITERM(it))
> continue;
> - if (iterm->id == pin)
> + if (it->id == pin) {
> + iterm = it;
> break;
> + }
> }
> }
>
> - if (iterm == NULL || iterm->id != pin)
> + if (iterm == NULL)
> return -EINVAL;
>
> memset(input, 0, sizeof(*input));
> --
> 2.17.1
>
--
Ricardo Ribalda
On Tue, 22 Mar 2022 15:10:21 +0200, Laurent Pinchart <[email protected]> wrote:
> > > Fixes: d5e90b7a6cd1c ("[media] uvcvideo: Move to video_ioctl2")
> > > Signed-off-by: Xiaomeng Tong <[email protected]>
> > > ---
> > > drivers/media/usb/uvc/uvc_v4l2.c | 20 +++++++++++++-------
> > > 1 file changed, 13 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
> > > index 711556d13d03..e7cdc01ad277 100644
> > > --- a/drivers/media/usb/uvc/uvc_v4l2.c
> > > +++ b/drivers/media/usb/uvc/uvc_v4l2.c
> > > @@ -871,6 +871,7 @@ static int uvc_ioctl_enum_input(struct file *file, void *fh,
> > > struct uvc_video_chain *chain = handle->chain;
> > > const struct uvc_entity *selector = chain->selector;
> > > struct uvc_entity *iterm = NULL;
> > > + struct uvc_entity *it;
> > > u32 index = input->index;
> > > int pin = 0;
> > >
> > > @@ -878,22 +879,27 @@ static int uvc_ioctl_enum_input(struct file *file, void *fh,
> > > (chain->dev->quirks & UVC_QUIRK_IGNORE_SELECTOR_UNIT)) {
> > > if (index != 0)
> > > return -EINVAL;
> > > - list_for_each_entry(iterm, &chain->entities, chain) {
> > > - if (UVC_ENTITY_IS_ITERM(iterm))
> > > + list_for_each_entry(it, &chain->entities, chain) {
> > > + if (UVC_ENTITY_IS_ITERM(it)) {
> > > + iterm = it;
> > > break;
> > > + }
> > > }
> > > - pin = iterm->id;
> > > + if (iterm)
> > > + pin = iterm->id;
>
> You can drop this, pin is not used anymore in the rest of the function.
>
> > > } else if (index < selector->bNrInPins) {
> > > pin = selector->baSourceID[index];
> > > - list_for_each_entry(iterm, &chain->entities, chain) {
> > > - if (!UVC_ENTITY_IS_ITERM(iterm))
> > > + list_for_each_entry(it, &chain->entities, chain) {
> > > + if (!UVC_ENTITY_IS_ITERM(it))
> > > continue;
> > > - if (iterm->id == pin)
> > > + if (it->id == pin) {
>
> And here you could use
> if (it->id == selector->baSourceID[index]) {
>
> and drop the local pin variable.
>
> If you're fine with those small changes I can handle them when applying
> the patch to my tree.
>
> Reviewed-by: Laurent Pinchart <[email protected]>
I'm fine with those small changes, thank you.
--
Xiaomeng Tong
On Tue, 22 Mar 2022 15:10:21 +0200, Laurent Pinchart wrote:
> > > Fixes: d5e90b7a6cd1c ("[media] uvcvideo: Move to video_ioctl2")
> > > Signed-off-by: Xiaomeng Tong <[email protected]>
> > > ---
> > > drivers/media/usb/uvc/uvc_v4l2.c | 20 +++++++++++++-------
> > > 1 file changed, 13 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
> > > index 711556d13d03..e7cdc01ad277 100644
> > > --- a/drivers/media/usb/uvc/uvc_v4l2.c
> > > +++ b/drivers/media/usb/uvc/uvc_v4l2.c
> > > @@ -871,6 +871,7 @@ static int uvc_ioctl_enum_input(struct file *file, void *fh,
> > > struct uvc_video_chain *chain = handle->chain;
> > > const struct uvc_entity *selector = chain->selector;
> > > struct uvc_entity *iterm = NULL;
> > > + struct uvc_entity *it;
> > > u32 index = input->index;
> > > int pin = 0;
> > >
> > > @@ -878,22 +879,27 @@ static int uvc_ioctl_enum_input(struct file *file, void *fh,
> > > (chain->dev->quirks & UVC_QUIRK_IGNORE_SELECTOR_UNIT)) {
> > > if (index != 0)
> > > return -EINVAL;
> > > - list_for_each_entry(iterm, &chain->entities, chain) {
> > > - if (UVC_ENTITY_IS_ITERM(iterm))
> > > + list_for_each_entry(it, &chain->entities, chain) {
> > > + if (UVC_ENTITY_IS_ITERM(it)) {
> > > + iterm = it;
> > > break;
> > > + }
> > > }
> > > - pin = iterm->id;
> > > + if (iterm)
> > > + pin = iterm->id;
>
> You can drop this, pin is not used anymore in the rest of the function.
>
> > > } else if (index < selector->bNrInPins) {
> > > pin = selector->baSourceID[index];
> > > - list_for_each_entry(iterm, &chain->entities, chain) {
> > > - if (!UVC_ENTITY_IS_ITERM(iterm))
> > > + list_for_each_entry(it, &chain->entities, chain) {
> > > + if (!UVC_ENTITY_IS_ITERM(it))
> > > continue;
> > > - if (iterm->id == pin)
> > > + if (it->id == pin) {
>
> And here you could use
> if (it->id == selector->baSourceID[index]) {
>
> and drop the local pin variable.
>
> If you're fine with those small changes I can handle them when applying
> the patch to my tree.
>
> Reviewed-by: Laurent Pinchart <[email protected]>
Thank you, i have resend a Patch v2 with changes as you suggested, please check it.
--
Xiaomeng Tong