* [PATCH] media: em28xx: fix corrupted list
@ 2021-07-06 14:50 Pavel Skripkin
2021-07-20 12:13 ` Hans Verkuil
0 siblings, 1 reply; 9+ messages in thread
From: Pavel Skripkin @ 2021-07-06 14:50 UTC (permalink / raw)
To: mchehab
Cc: linux-media, linux-kernel, Pavel Skripkin, syzbot+a6969ef522a36d3344c9
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: syzbot+a6969ef522a36d3344c9@syzkaller.appspotmail.com
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
---
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
^ permalink raw reply related [flat|nested] 9+ messages in thread* Re: [PATCH] media: em28xx: fix corrupted list 2021-07-06 14:50 [PATCH] media: em28xx: fix corrupted list Pavel Skripkin @ 2021-07-20 12:13 ` Hans Verkuil 2021-07-21 12:21 ` Pavel Skripkin 0 siblings, 1 reply; 9+ messages in thread From: Hans Verkuil @ 2021-07-20 12:13 UTC (permalink / raw) To: Pavel Skripkin, mchehab Cc: linux-media, linux-kernel, syzbot+a6969ef522a36d3344c9 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: syzbot+a6969ef522a36d3344c9@syzkaller.appspotmail.com > Signed-off-by: Pavel Skripkin <paskripkin@gmail.com> > --- > 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); > ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] media: em28xx: fix corrupted list 2021-07-20 12:13 ` Hans Verkuil @ 2021-07-21 12:21 ` Pavel Skripkin 2021-07-21 12:25 ` Hans Verkuil 0 siblings, 1 reply; 9+ messages in thread From: Pavel Skripkin @ 2021-07-21 12:21 UTC (permalink / raw) To: Hans Verkuil Cc: mchehab, linux-media, linux-kernel, syzbot+a6969ef522a36d3344c9 On Tue, 20 Jul 2021 14:13:13 +0200 Hans Verkuil <hverkuil@xs4all.nl> 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: > > syzbot+a6969ef522a36d3344c9@syzkaller.appspotmail.com > > Signed-off-by: Pavel Skripkin <paskripkin@gmail.com> --- > > 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 ^ permalink raw reply related [flat|nested] 9+ messages in thread
* Re: [PATCH] media: em28xx: fix corrupted list 2021-07-21 12:21 ` Pavel Skripkin @ 2021-07-21 12:25 ` Hans Verkuil 2021-07-21 19:43 ` [PATCH v2] media: em28xx: add missing em28xx_close_extension Pavel Skripkin 0 siblings, 1 reply; 9+ messages in thread From: Hans Verkuil @ 2021-07-21 12:25 UTC (permalink / raw) To: Pavel Skripkin Cc: mchehab, linux-media, linux-kernel, syzbot+a6969ef522a36d3344c9 On 21/07/2021 14:21, Pavel Skripkin wrote: > On Tue, 20 Jul 2021 14:13:13 +0200 > Hans Verkuil <hverkuil@xs4all.nl> 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: >>> syzbot+a6969ef522a36d3344c9@syzkaller.appspotmail.com >>> Signed-off-by: Pavel Skripkin <paskripkin@gmail.com> --- >>> 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 > ^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH v2] media: em28xx: add missing em28xx_close_extension 2021-07-21 12:25 ` Hans Verkuil @ 2021-07-21 19:43 ` Pavel Skripkin 2021-07-29 9:45 ` Hans Verkuil 0 siblings, 1 reply; 9+ messages in thread From: Pavel Skripkin @ 2021-07-21 19:43 UTC (permalink / raw) To: mchehab, hverkuil Cc: linux-media, linux-kernel, Pavel Skripkin, syzbot+a6969ef522a36d3344c9 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: syzbot+a6969ef522a36d3344c9@syzkaller.appspotmail.com Signed-off-by: Pavel Skripkin <paskripkin@gmail.com> --- 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 ^ permalink raw reply related [flat|nested] 9+ messages in thread
* Re: [PATCH v2] media: em28xx: add missing em28xx_close_extension 2021-07-21 19:43 ` [PATCH v2] media: em28xx: add missing em28xx_close_extension Pavel Skripkin @ 2021-07-29 9:45 ` Hans Verkuil 2021-07-29 12:45 ` Pavel Skripkin 0 siblings, 1 reply; 9+ messages in thread From: Hans Verkuil @ 2021-07-29 9:45 UTC (permalink / raw) To: Pavel Skripkin, mchehab Cc: linux-media, linux-kernel, syzbot+a6969ef522a36d3344c9 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: syzbot+a6969ef522a36d3344c9@syzkaller.appspotmail.com > Signed-off-by: Pavel Skripkin <paskripkin@gmail.com> > --- > > 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) { > ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH v2] media: em28xx: add missing em28xx_close_extension 2021-07-29 9:45 ` Hans Verkuil @ 2021-07-29 12:45 ` Pavel Skripkin 2021-07-29 13:40 ` Hans Verkuil 0 siblings, 1 reply; 9+ messages in thread From: Pavel Skripkin @ 2021-07-29 12:45 UTC (permalink / raw) To: Hans Verkuil Cc: mchehab, linux-media, linux-kernel, syzbot+a6969ef522a36d3344c9 On Thu, 29 Jul 2021 11:45:19 +0200 Hans Verkuil <hverkuil@xs4all.nl> 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: > > syzbot+a6969ef522a36d3344c9@syzkaller.appspotmail.com > > Signed-off-by: Pavel Skripkin <paskripkin@gmail.com> --- > > > > 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 ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH v2] media: em28xx: add missing em28xx_close_extension 2021-07-29 12:45 ` Pavel Skripkin @ 2021-07-29 13:40 ` Hans Verkuil 2021-07-29 20:23 ` [PATCH v3] " Pavel Skripkin 0 siblings, 1 reply; 9+ messages in thread From: Hans Verkuil @ 2021-07-29 13:40 UTC (permalink / raw) To: Pavel Skripkin Cc: mchehab, linux-media, linux-kernel, syzbot+a6969ef522a36d3344c9 On 29/07/2021 14:45, Pavel Skripkin wrote: > On Thu, 29 Jul 2021 11:45:19 +0200 > Hans Verkuil <hverkuil@xs4all.nl> 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: >>> syzbot+a6969ef522a36d3344c9@syzkaller.appspotmail.com >>> Signed-off-by: Pavel Skripkin <paskripkin@gmail.com> --- >>> >>> 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 > > ^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH v3] media: em28xx: add missing em28xx_close_extension 2021-07-29 13:40 ` Hans Verkuil @ 2021-07-29 20:23 ` Pavel Skripkin 0 siblings, 0 replies; 9+ messages in thread From: Pavel Skripkin @ 2021-07-29 20:23 UTC (permalink / raw) To: mchehab, hverkuil Cc: linux-media, linux-kernel, Pavel Skripkin, syzbot+a6969ef522a36d3344c9 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: syzbot+a6969ef522a36d3344c9@syzkaller.appspotmail.com Signed-off-by: Pavel Skripkin <paskripkin@gmail.com> --- 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 ^ permalink raw reply related [flat|nested] 9+ messages in thread
end of thread, other threads:[~2021-07-29 20:23 UTC | newest] Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2021-07-06 14:50 [PATCH] media: em28xx: fix corrupted list Pavel Skripkin 2021-07-20 12:13 ` Hans Verkuil 2021-07-21 12:21 ` Pavel Skripkin 2021-07-21 12:25 ` Hans Verkuil 2021-07-21 19:43 ` [PATCH v2] media: em28xx: add missing em28xx_close_extension Pavel Skripkin 2021-07-29 9:45 ` Hans Verkuil 2021-07-29 12:45 ` Pavel Skripkin 2021-07-29 13:40 ` Hans Verkuil 2021-07-29 20:23 ` [PATCH v3] " Pavel Skripkin
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