Syzbot reported corrupted list in em28xx driver. The problem was in
non-reinitialized lists on disconnect. Since all 2 lists are global
variables and driver can be connected and disconnected many times we
should call INIT_LIST_HEAD() in .disconnect method to prevent corrupted
list entries.
Fixes: 1a23f81b7dc3 ("V4L/DVB (9979): em28xx: move usb probe code to a proper place")
Reported-by: [email protected]
Signed-off-by: Pavel Skripkin <[email protected]>
---
drivers/media/usb/em28xx/em28xx-cards.c | 2 ++
drivers/media/usb/em28xx/em28xx-core.c | 6 ++++++
drivers/media/usb/em28xx/em28xx.h | 1 +
3 files changed, 9 insertions(+)
diff --git a/drivers/media/usb/em28xx/em28xx-cards.c b/drivers/media/usb/em28xx/em28xx-cards.c
index ba9292e2a587..8b1ff79c37a0 100644
--- a/drivers/media/usb/em28xx/em28xx-cards.c
+++ b/drivers/media/usb/em28xx/em28xx-cards.c
@@ -4148,6 +4148,8 @@ static void em28xx_usb_disconnect(struct usb_interface *intf)
dev->dev_next = NULL;
}
kref_put(&dev->ref, em28xx_free_device);
+
+ em28xx_reset_lists();
}
static int em28xx_usb_suspend(struct usb_interface *intf,
diff --git a/drivers/media/usb/em28xx/em28xx-core.c b/drivers/media/usb/em28xx/em28xx-core.c
index 584fa400cd7d..03970ed00dba 100644
--- a/drivers/media/usb/em28xx/em28xx-core.c
+++ b/drivers/media/usb/em28xx/em28xx-core.c
@@ -1131,6 +1131,12 @@ void em28xx_init_extension(struct em28xx *dev)
mutex_unlock(&em28xx_devlist_mutex);
}
+void em28xx_reset_lists(void)
+{
+ INIT_LIST_HEAD(&em28xx_devlist);
+ INIT_LIST_HEAD(&em28xx_extension_devlist);
+}
+
void em28xx_close_extension(struct em28xx *dev)
{
const struct em28xx_ops *ops = NULL;
diff --git a/drivers/media/usb/em28xx/em28xx.h b/drivers/media/usb/em28xx/em28xx.h
index ab167cd1f400..73caaaa398d3 100644
--- a/drivers/media/usb/em28xx/em28xx.h
+++ b/drivers/media/usb/em28xx/em28xx.h
@@ -835,6 +835,7 @@ void em28xx_stop_urbs(struct em28xx *dev);
int em28xx_set_mode(struct em28xx *dev, enum em28xx_mode set_mode);
int em28xx_gpio_set(struct em28xx *dev, const struct em28xx_reg_seq *gpio);
int em28xx_register_extension(struct em28xx_ops *dev);
+void em28xx_reset_lists(void);
void em28xx_unregister_extension(struct em28xx_ops *dev);
void em28xx_init_extension(struct em28xx *dev);
void em28xx_close_extension(struct em28xx *dev);
--
2.32.0
On 06/07/2021 16:50, Pavel Skripkin wrote:
> Syzbot reported corrupted list in em28xx driver. The problem was in
> non-reinitialized lists on disconnect. Since all 2 lists are global
> variables and driver can be connected and disconnected many times we
> should call INIT_LIST_HEAD() in .disconnect method to prevent corrupted
> list entries.
>
> Fixes: 1a23f81b7dc3 ("V4L/DVB (9979): em28xx: move usb probe code to a proper place")
> Reported-by: [email protected]
> Signed-off-by: Pavel Skripkin <[email protected]>
> ---
> drivers/media/usb/em28xx/em28xx-cards.c | 2 ++
> drivers/media/usb/em28xx/em28xx-core.c | 6 ++++++
> drivers/media/usb/em28xx/em28xx.h | 1 +
> 3 files changed, 9 insertions(+)
>
> diff --git a/drivers/media/usb/em28xx/em28xx-cards.c b/drivers/media/usb/em28xx/em28xx-cards.c
> index ba9292e2a587..8b1ff79c37a0 100644
> --- a/drivers/media/usb/em28xx/em28xx-cards.c
> +++ b/drivers/media/usb/em28xx/em28xx-cards.c
> @@ -4148,6 +4148,8 @@ static void em28xx_usb_disconnect(struct usb_interface *intf)
> dev->dev_next = NULL;
> }
> kref_put(&dev->ref, em28xx_free_device);
> +
> + em28xx_reset_lists();
> }
>
> static int em28xx_usb_suspend(struct usb_interface *intf,
> diff --git a/drivers/media/usb/em28xx/em28xx-core.c b/drivers/media/usb/em28xx/em28xx-core.c
> index 584fa400cd7d..03970ed00dba 100644
> --- a/drivers/media/usb/em28xx/em28xx-core.c
> +++ b/drivers/media/usb/em28xx/em28xx-core.c
> @@ -1131,6 +1131,12 @@ void em28xx_init_extension(struct em28xx *dev)
> mutex_unlock(&em28xx_devlist_mutex);
> }
>
> +void em28xx_reset_lists(void)
> +{
> + INIT_LIST_HEAD(&em28xx_devlist);
> + INIT_LIST_HEAD(&em28xx_extension_devlist);
This needs a mutex_lock(&em28xx_devlist_mutex);
But actually, I don't think this is right: if there are multiple em28xx
devices, then I think if you disconnect one, then the other is - with this
code - also removed from the list.
Can you give a link to the actual syzbot bug? I'm not at all sure you are
fixing the right thing here.
Regards,
Hans
> +}
> +
> void em28xx_close_extension(struct em28xx *dev)
> {
> const struct em28xx_ops *ops = NULL;
> diff --git a/drivers/media/usb/em28xx/em28xx.h b/drivers/media/usb/em28xx/em28xx.h
> index ab167cd1f400..73caaaa398d3 100644
> --- a/drivers/media/usb/em28xx/em28xx.h
> +++ b/drivers/media/usb/em28xx/em28xx.h
> @@ -835,6 +835,7 @@ void em28xx_stop_urbs(struct em28xx *dev);
> int em28xx_set_mode(struct em28xx *dev, enum em28xx_mode set_mode);
> int em28xx_gpio_set(struct em28xx *dev, const struct em28xx_reg_seq *gpio);
> int em28xx_register_extension(struct em28xx_ops *dev);
> +void em28xx_reset_lists(void);
> void em28xx_unregister_extension(struct em28xx_ops *dev);
> void em28xx_init_extension(struct em28xx *dev);
> void em28xx_close_extension(struct em28xx *dev);
>
On 21/07/2021 14:21, Pavel Skripkin wrote:
> On Tue, 20 Jul 2021 14:13:13 +0200
> Hans Verkuil <[email protected]> wrote:
>
>> On 06/07/2021 16:50, Pavel Skripkin wrote:
>>> Syzbot reported corrupted list in em28xx driver. The problem was in
>>> non-reinitialized lists on disconnect. Since all 2 lists are global
>>> variables and driver can be connected and disconnected many times we
>>> should call INIT_LIST_HEAD() in .disconnect method to prevent
>>> corrupted list entries.
>>>
>>> Fixes: 1a23f81b7dc3 ("V4L/DVB (9979): em28xx: move usb probe code
>>> to a proper place") Reported-by:
>>> [email protected]
>>> Signed-off-by: Pavel Skripkin <[email protected]> ---
>>> drivers/media/usb/em28xx/em28xx-cards.c | 2 ++
>>> drivers/media/usb/em28xx/em28xx-core.c | 6 ++++++
>>> drivers/media/usb/em28xx/em28xx.h | 1 +
>>> 3 files changed, 9 insertions(+)
>>>
>>> diff --git a/drivers/media/usb/em28xx/em28xx-cards.c
>>> b/drivers/media/usb/em28xx/em28xx-cards.c index
>>> ba9292e2a587..8b1ff79c37a0 100644 ---
>>> a/drivers/media/usb/em28xx/em28xx-cards.c +++
>>> b/drivers/media/usb/em28xx/em28xx-cards.c @@ -4148,6 +4148,8 @@
>>> static void em28xx_usb_disconnect(struct usb_interface *intf)
>>> dev->dev_next = NULL; }
>>> kref_put(&dev->ref, em28xx_free_device);
>>> +
>>> + em28xx_reset_lists();
>>> }
>>>
>>> static int em28xx_usb_suspend(struct usb_interface *intf,
>>> diff --git a/drivers/media/usb/em28xx/em28xx-core.c
>>> b/drivers/media/usb/em28xx/em28xx-core.c index
>>> 584fa400cd7d..03970ed00dba 100644 ---
>>> a/drivers/media/usb/em28xx/em28xx-core.c +++
>>> b/drivers/media/usb/em28xx/em28xx-core.c @@ -1131,6 +1131,12 @@
>>> void em28xx_init_extension(struct em28xx *dev)
>>> mutex_unlock(&em28xx_devlist_mutex); }
>>>
>>> +void em28xx_reset_lists(void)
>>> +{
>>> + INIT_LIST_HEAD(&em28xx_devlist);
>>> + INIT_LIST_HEAD(&em28xx_extension_devlist);
>>
>> This needs a mutex_lock(&em28xx_devlist_mutex);
>>
>> But actually, I don't think this is right: if there are multiple
>> em28xx devices, then I think if you disconnect one, then the other is
>> - with this code - also removed from the list.
>>
>> Can you give a link to the actual syzbot bug? I'm not at all sure you
>> are fixing the right thing here.
>
> Hi, Hans!
>
> I guess, I missed my coffee that morning, sorry :) This patch looks
> complety wrong, of course.
>
> I've took a close look at this bug one more time, and I found the true
> root case of this bug.
>
> If em28xx dev has dev_next pointer we need to close dev->next extension
> on disconnect to avoid UAF and corrupted list bug. So, something like
> this should work:
>
> diff --git a/drivers/media/usb/em28xx/em28xx-cards.c b/drivers/media/usb/em28xx/em28xx-cards.c
> index c1e0dccb7408..d56b040e1bd7 100644
> --- a/drivers/media/usb/em28xx/em28xx-cards.c
> +++ b/drivers/media/usb/em28xx/em28xx-cards.c
> @@ -4139,8 +4139,10 @@ static void em28xx_usb_disconnect(struct usb_interface *intf)
>
> em28xx_close_extension(dev);
>
> - if (dev->dev_next)
> + if (dev->dev_next) {
> em28xx_release_resources(dev->dev_next);
> + em28xx_close_extension(dev->dev_next);
> + }
> em28xx_release_resources(dev);
>
> if (dev->dev_next) {
>
> How to You feel about it? I am going to send this patch for syzbot
> testing
That looks a lot saner :-)
>
>
> Syzbot link:
> https://syzkaller.appspot.com/bug?id=3609bbf45bf63a8f6032f330eb3d34f51cc81493
>
>
> Again, sorry for v1 patch, I don't know how I came up with this fix :(
No problem, just post a v2 if syzbot passes.
Regards,
Hans
>
>
>
> With regards,
> Pavel Skripkin
>
On Tue, 20 Jul 2021 14:13:13 +0200
Hans Verkuil <[email protected]> wrote:
> On 06/07/2021 16:50, Pavel Skripkin wrote:
> > Syzbot reported corrupted list in em28xx driver. The problem was in
> > non-reinitialized lists on disconnect. Since all 2 lists are global
> > variables and driver can be connected and disconnected many times we
> > should call INIT_LIST_HEAD() in .disconnect method to prevent
> > corrupted list entries.
> >
> > Fixes: 1a23f81b7dc3 ("V4L/DVB (9979): em28xx: move usb probe code
> > to a proper place") Reported-by:
> > [email protected]
> > Signed-off-by: Pavel Skripkin <[email protected]> ---
> > drivers/media/usb/em28xx/em28xx-cards.c | 2 ++
> > drivers/media/usb/em28xx/em28xx-core.c | 6 ++++++
> > drivers/media/usb/em28xx/em28xx.h | 1 +
> > 3 files changed, 9 insertions(+)
> >
> > diff --git a/drivers/media/usb/em28xx/em28xx-cards.c
> > b/drivers/media/usb/em28xx/em28xx-cards.c index
> > ba9292e2a587..8b1ff79c37a0 100644 ---
> > a/drivers/media/usb/em28xx/em28xx-cards.c +++
> > b/drivers/media/usb/em28xx/em28xx-cards.c @@ -4148,6 +4148,8 @@
> > static void em28xx_usb_disconnect(struct usb_interface *intf)
> > dev->dev_next = NULL; }
> > kref_put(&dev->ref, em28xx_free_device);
> > +
> > + em28xx_reset_lists();
> > }
> >
> > static int em28xx_usb_suspend(struct usb_interface *intf,
> > diff --git a/drivers/media/usb/em28xx/em28xx-core.c
> > b/drivers/media/usb/em28xx/em28xx-core.c index
> > 584fa400cd7d..03970ed00dba 100644 ---
> > a/drivers/media/usb/em28xx/em28xx-core.c +++
> > b/drivers/media/usb/em28xx/em28xx-core.c @@ -1131,6 +1131,12 @@
> > void em28xx_init_extension(struct em28xx *dev)
> > mutex_unlock(&em28xx_devlist_mutex); }
> >
> > +void em28xx_reset_lists(void)
> > +{
> > + INIT_LIST_HEAD(&em28xx_devlist);
> > + INIT_LIST_HEAD(&em28xx_extension_devlist);
>
> This needs a mutex_lock(&em28xx_devlist_mutex);
>
> But actually, I don't think this is right: if there are multiple
> em28xx devices, then I think if you disconnect one, then the other is
> - with this code - also removed from the list.
>
> Can you give a link to the actual syzbot bug? I'm not at all sure you
> are fixing the right thing here.
Hi, Hans!
I guess, I missed my coffee that morning, sorry :) This patch looks
complety wrong, of course.
I've took a close look at this bug one more time, and I found the true
root case of this bug.
If em28xx dev has dev_next pointer we need to close dev->next extension
on disconnect to avoid UAF and corrupted list bug. So, something like
this should work:
diff --git a/drivers/media/usb/em28xx/em28xx-cards.c b/drivers/media/usb/em28xx/em28xx-cards.c
index c1e0dccb7408..d56b040e1bd7 100644
--- a/drivers/media/usb/em28xx/em28xx-cards.c
+++ b/drivers/media/usb/em28xx/em28xx-cards.c
@@ -4139,8 +4139,10 @@ static void em28xx_usb_disconnect(struct usb_interface *intf)
em28xx_close_extension(dev);
- if (dev->dev_next)
+ if (dev->dev_next) {
em28xx_release_resources(dev->dev_next);
+ em28xx_close_extension(dev->dev_next);
+ }
em28xx_release_resources(dev);
if (dev->dev_next) {
How to You feel about it? I am going to send this patch for syzbot
testing
Syzbot link:
https://syzkaller.appspot.com/bug?id=3609bbf45bf63a8f6032f330eb3d34f51cc81493
Again, sorry for v1 patch, I don't know how I came up with this fix :(
With regards,
Pavel Skripkin
If em28xx dev has ->dev_next pointer, we need to delete dev_next list node
from em28xx_extension_devlist on disconnect to avoid UAF bugs and
corrupted list bugs, since driver frees this pointer on disconnect.
Fixes: 1a23f81b7dc3 ("V4L/DVB (9979): em28xx: move usb probe code to a proper place")
Reported-and-tested-by: [email protected]
Signed-off-by: Pavel Skripkin <[email protected]>
---
Changes in v2:
Previous patch was completely broken. I've done some debugging
again and found true root case of the reported bug.
---
drivers/media/usb/em28xx/em28xx-cards.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/media/usb/em28xx/em28xx-cards.c b/drivers/media/usb/em28xx/em28xx-cards.c
index c1e0dccb7408..d56b040e1bd7 100644
--- a/drivers/media/usb/em28xx/em28xx-cards.c
+++ b/drivers/media/usb/em28xx/em28xx-cards.c
@@ -4139,8 +4139,10 @@ static void em28xx_usb_disconnect(struct usb_interface *intf)
em28xx_close_extension(dev);
- if (dev->dev_next)
+ if (dev->dev_next) {
em28xx_release_resources(dev->dev_next);
+ em28xx_close_extension(dev->dev_next);
+ }
em28xx_release_resources(dev);
if (dev->dev_next) {
--
2.32.0
On 21/07/2021 21:43, Pavel Skripkin wrote:
> If em28xx dev has ->dev_next pointer, we need to delete dev_next list node
> from em28xx_extension_devlist on disconnect to avoid UAF bugs and
> corrupted list bugs, since driver frees this pointer on disconnect.
>
> Fixes: 1a23f81b7dc3 ("V4L/DVB (9979): em28xx: move usb probe code to a proper place")
> Reported-and-tested-by: [email protected]
> Signed-off-by: Pavel Skripkin <[email protected]>
> ---
>
> Changes in v2:
> Previous patch was completely broken. I've done some debugging
> again and found true root case of the reported bug.
>
> ---
> drivers/media/usb/em28xx/em28xx-cards.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/media/usb/em28xx/em28xx-cards.c b/drivers/media/usb/em28xx/em28xx-cards.c
> index c1e0dccb7408..d56b040e1bd7 100644
> --- a/drivers/media/usb/em28xx/em28xx-cards.c
> +++ b/drivers/media/usb/em28xx/em28xx-cards.c
> @@ -4139,8 +4139,10 @@ static void em28xx_usb_disconnect(struct usb_interface *intf)
>
> em28xx_close_extension(dev);
>
> - if (dev->dev_next)
> + if (dev->dev_next) {
> em28xx_release_resources(dev->dev_next);
> + em28xx_close_extension(dev->dev_next);
Wouldn't it be better to swap these two?
That order is also used for em28xx_close_extension(dev) and em28xx_release_resources(dev).
You do need to store dev->dev_next in a temp variable, though.
Regards,
Hans
> + }
> em28xx_release_resources(dev);
>
> if (dev->dev_next) {
>
On Thu, 29 Jul 2021 11:45:19 +0200
Hans Verkuil <[email protected]> wrote:
> On 21/07/2021 21:43, Pavel Skripkin wrote:
> > If em28xx dev has ->dev_next pointer, we need to delete dev_next
> > list node from em28xx_extension_devlist on disconnect to avoid UAF
> > bugs and corrupted list bugs, since driver frees this pointer on
> > disconnect.
> >
> > Fixes: 1a23f81b7dc3 ("V4L/DVB (9979): em28xx: move usb probe code
> > to a proper place") Reported-and-tested-by:
> > [email protected]
> > Signed-off-by: Pavel Skripkin <[email protected]> ---
> >
> > Changes in v2:
> > Previous patch was completely broken. I've done some
> > debugging again and found true root case of the reported bug.
> >
> > ---
> > drivers/media/usb/em28xx/em28xx-cards.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/media/usb/em28xx/em28xx-cards.c
> > b/drivers/media/usb/em28xx/em28xx-cards.c index
> > c1e0dccb7408..d56b040e1bd7 100644 ---
> > a/drivers/media/usb/em28xx/em28xx-cards.c +++
> > b/drivers/media/usb/em28xx/em28xx-cards.c @@ -4139,8 +4139,10 @@
> > static void em28xx_usb_disconnect(struct usb_interface *intf)
> > em28xx_close_extension(dev);
> >
> > - if (dev->dev_next)
> > + if (dev->dev_next) {
> > em28xx_release_resources(dev->dev_next);
> > + em28xx_close_extension(dev->dev_next);
>
> Wouldn't it be better to swap these two?
>
> That order is also used for em28xx_close_extension(dev) and
> em28xx_release_resources(dev).
>
> You do need to store dev->dev_next in a temp variable, though.
>
Hi, Hans!
I don't understand why I need to store dev->dev_next in a temp
variable. I don't see code in em28xx_release_resources() or
em28xx_close_extension() that zeroes this pointer.
With regards,
Pavel Skripkin
On 29/07/2021 14:45, Pavel Skripkin wrote:
> On Thu, 29 Jul 2021 11:45:19 +0200
> Hans Verkuil <[email protected]> wrote:
>
>> On 21/07/2021 21:43, Pavel Skripkin wrote:
>>> If em28xx dev has ->dev_next pointer, we need to delete dev_next
>>> list node from em28xx_extension_devlist on disconnect to avoid UAF
>>> bugs and corrupted list bugs, since driver frees this pointer on
>>> disconnect.
>>>
>>> Fixes: 1a23f81b7dc3 ("V4L/DVB (9979): em28xx: move usb probe code
>>> to a proper place") Reported-and-tested-by:
>>> [email protected]
>>> Signed-off-by: Pavel Skripkin <[email protected]> ---
>>>
>>> Changes in v2:
>>> Previous patch was completely broken. I've done some
>>> debugging again and found true root case of the reported bug.
>>>
>>> ---
>>> drivers/media/usb/em28xx/em28xx-cards.c | 4 +++-
>>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/media/usb/em28xx/em28xx-cards.c
>>> b/drivers/media/usb/em28xx/em28xx-cards.c index
>>> c1e0dccb7408..d56b040e1bd7 100644 ---
>>> a/drivers/media/usb/em28xx/em28xx-cards.c +++
>>> b/drivers/media/usb/em28xx/em28xx-cards.c @@ -4139,8 +4139,10 @@
>>> static void em28xx_usb_disconnect(struct usb_interface *intf)
>>> em28xx_close_extension(dev);
>>>
>>> - if (dev->dev_next)
>>> + if (dev->dev_next) {
>>> em28xx_release_resources(dev->dev_next);
>>> + em28xx_close_extension(dev->dev_next);
>>
>> Wouldn't it be better to swap these two?
>>
>> That order is also used for em28xx_close_extension(dev) and
>> em28xx_release_resources(dev).
>>
>> You do need to store dev->dev_next in a temp variable, though.
>>
>
> Hi, Hans!
>
> I don't understand why I need to store dev->dev_next in a temp
> variable. I don't see code in em28xx_release_resources() or
> em28xx_close_extension() that zeroes this pointer.
Apologies for the confusion, just ignore that bit. I misunderstood
what dev_next was for.
So check if swapping these two lines passes syzbot, and then that's
the final version.
Regards,
Hans
>
>
>
> With regards,
> Pavel Skripkin
>
>
If em28xx dev has ->dev_next pointer, we need to delete ->dev_next list
node from em28xx_extension_devlist on disconnect to avoid UAF bugs and
corrupted list bugs, since driver frees this pointer on disconnect.
Fixes: 1a23f81b7dc3 ("V4L/DVB (9979): em28xx: move usb probe code to a proper place")
Reported-and-tested-by: [email protected]
Signed-off-by: Pavel Skripkin <[email protected]>
---
Changes in v3:
Changed order of em28xx_close_extension() and
em28xx_release_resources() as Hans suggested
Changes in v2:
Previous patch was completely broken. I've done some debugging
again and found true root case of the reported bug.
---
drivers/media/usb/em28xx/em28xx-cards.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/media/usb/em28xx/em28xx-cards.c b/drivers/media/usb/em28xx/em28xx-cards.c
index c1e0dccb7408..948e22e29b42 100644
--- a/drivers/media/usb/em28xx/em28xx-cards.c
+++ b/drivers/media/usb/em28xx/em28xx-cards.c
@@ -4139,8 +4139,11 @@ static void em28xx_usb_disconnect(struct usb_interface *intf)
em28xx_close_extension(dev);
- if (dev->dev_next)
+ if (dev->dev_next) {
+ em28xx_close_extension(dev->dev_next);
em28xx_release_resources(dev->dev_next);
+ }
+
em28xx_release_resources(dev);
if (dev->dev_next) {
--
2.32.0