* Re: [PATCH] pxa3xx-gcu: Fix integer overflow in pxa3xx_gcu_write
@ 2022-09-20 6:02 Dan Carpenter
2022-09-20 6:13 ` Dan Carpenter
0 siblings, 1 reply; 4+ messages in thread
From: Dan Carpenter @ 2022-09-20 6:02 UTC (permalink / raw)
To: Hyunwoo Kim, deller, linux-fbdev, Masami Ichikawa, cip-dev,
Harshit Mogalapalli
On Mon, Jun 20, 2022 at 07:00:10AM -0700, Hyunwoo Kim wrote:
> In pxa3xx_gcu_write, a count parameter of
> type size_t is passed to words of type int.
> Then, copy_from_user may cause a heap overflow because
> it is used as the third argument of copy_from_user.
>
> Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
> ---
> drivers/video/fbdev/pxa3xx-gcu.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/video/fbdev/pxa3xx-gcu.c b/drivers/video/fbdev/pxa3xx-gcu.c
> index 043cc8f9ef1c..c3cd1e1cc01b 100644
> --- a/drivers/video/fbdev/pxa3xx-gcu.c
> +++ b/drivers/video/fbdev/pxa3xx-gcu.c
> @@ -381,7 +381,7 @@ pxa3xx_gcu_write(struct file *file, const char *buff,
> struct pxa3xx_gcu_batch *buffer;
> struct pxa3xx_gcu_priv *priv = to_pxa3xx_gcu_priv(file);
>
> - int words = count / 4;
> + size_t words = count / 4;
The count variable is actually capped at MAX_RW_COUNT in vfs_write()
so "words" cannot be negative. This patch helps clean up the code but
it does not affect run time.
This is CVE-2022-39842.
regards,
dan carpenter
PS: The other relavant code for people looking for integer overflows in
read/write functions is in rw_verify_area(). That function prevents a
lot of suspicious looking driver code from being exploitable.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] pxa3xx-gcu: Fix integer overflow in pxa3xx_gcu_write
2022-09-20 6:02 [PATCH] pxa3xx-gcu: Fix integer overflow in pxa3xx_gcu_write Dan Carpenter
@ 2022-09-20 6:13 ` Dan Carpenter
2022-09-20 6:22 ` Hyunwoo Kim
0 siblings, 1 reply; 4+ messages in thread
From: Dan Carpenter @ 2022-09-20 6:13 UTC (permalink / raw)
To: Hyunwoo Kim, deller, linux-fbdev, Masami Ichikawa, cip-dev,
Harshit Mogalapalli
On Tue, Sep 20, 2022 at 09:02:34AM +0300, Dan Carpenter wrote:
> On Mon, Jun 20, 2022 at 07:00:10AM -0700, Hyunwoo Kim wrote:
> > In pxa3xx_gcu_write, a count parameter of
> > type size_t is passed to words of type int.
> > Then, copy_from_user may cause a heap overflow because
> > it is used as the third argument of copy_from_user.
> >
> > Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
> > ---
> > drivers/video/fbdev/pxa3xx-gcu.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/video/fbdev/pxa3xx-gcu.c b/drivers/video/fbdev/pxa3xx-gcu.c
> > index 043cc8f9ef1c..c3cd1e1cc01b 100644
> > --- a/drivers/video/fbdev/pxa3xx-gcu.c
> > +++ b/drivers/video/fbdev/pxa3xx-gcu.c
> > @@ -381,7 +381,7 @@ pxa3xx_gcu_write(struct file *file, const char *buff,
> > struct pxa3xx_gcu_batch *buffer;
> > struct pxa3xx_gcu_priv *priv = to_pxa3xx_gcu_priv(file);
> >
> > - int words = count / 4;
> > + size_t words = count / 4;
>
> The count variable is actually capped at MAX_RW_COUNT in vfs_write()
> so "words" cannot be negative. This patch helps clean up the code but
> it does not affect run time.
Btw, the other thing which prevents this from being expliotable is that
if you pass a negative value to copy_from_user() it will not copy
anything because of the check in check_copy_size(). See commit
6d13de1489b6 ("uaccess: disallow > INT_MAX copy sizes").
Linus has sort of gotten annoyed with me before for pointing this stuff
out because it seemed like maybe I wasn't properly grateful to people
auditing the code and fixing bugs. I am grateful. This patch is
totally the correct thing to do. It's just that it's not really
exploitable as described in the commit message.
regards,
dan carpenter
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] pxa3xx-gcu: Fix integer overflow in pxa3xx_gcu_write
2022-09-20 6:13 ` Dan Carpenter
@ 2022-09-20 6:22 ` Hyunwoo Kim
2022-09-20 7:12 ` Dan Carpenter
0 siblings, 1 reply; 4+ messages in thread
From: Hyunwoo Kim @ 2022-09-20 6:22 UTC (permalink / raw)
To: Dan Carpenter
Cc: deller, linux-fbdev, Masami Ichikawa, cip-dev,
Harshit Mogalapalli
On Tue, Sep 20, 2022 at 09:13:31AM +0300, Dan Carpenter wrote:
> On Tue, Sep 20, 2022 at 09:02:34AM +0300, Dan Carpenter wrote:
> > On Mon, Jun 20, 2022 at 07:00:10AM -0700, Hyunwoo Kim wrote:
> > > In pxa3xx_gcu_write, a count parameter of
> > > type size_t is passed to words of type int.
> > > Then, copy_from_user may cause a heap overflow because
> > > it is used as the third argument of copy_from_user.
> > >
> > > Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
> > > ---
> > > drivers/video/fbdev/pxa3xx-gcu.c | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/video/fbdev/pxa3xx-gcu.c b/drivers/video/fbdev/pxa3xx-gcu.c
> > > index 043cc8f9ef1c..c3cd1e1cc01b 100644
> > > --- a/drivers/video/fbdev/pxa3xx-gcu.c
> > > +++ b/drivers/video/fbdev/pxa3xx-gcu.c
> > > @@ -381,7 +381,7 @@ pxa3xx_gcu_write(struct file *file, const char *buff,
> > > struct pxa3xx_gcu_batch *buffer;
> > > struct pxa3xx_gcu_priv *priv = to_pxa3xx_gcu_priv(file);
> > >
> > > - int words = count / 4;
> > > + size_t words = count / 4;
> >
> > The count variable is actually capped at MAX_RW_COUNT in vfs_write()
> > so "words" cannot be negative. This patch helps clean up the code but
> > it does not affect run time.
>
> Btw, the other thing which prevents this from being expliotable is that
> if you pass a negative value to copy_from_user() it will not copy
> anything because of the check in check_copy_size(). See commit
> 6d13de1489b6 ("uaccess: disallow > INT_MAX copy sizes").
>
> Linus has sort of gotten annoyed with me before for pointing this stuff
> out because it seemed like maybe I wasn't properly grateful to people
> auditing the code and fixing bugs. I am grateful. This patch is
> totally the correct thing to do. It's just that it's not really
> exploitable as described in the commit message.
I found the code that might have the vulnerability, and submitted a patch without actually debugging it.
This is entirely my fault. sorry.
Should I submit a fix patch that fixes the commit message?
Sorry again.
Regards,
Hyunwoo Kim.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] pxa3xx-gcu: Fix integer overflow in pxa3xx_gcu_write
2022-09-20 6:22 ` Hyunwoo Kim
@ 2022-09-20 7:12 ` Dan Carpenter
0 siblings, 0 replies; 4+ messages in thread
From: Dan Carpenter @ 2022-09-20 7:12 UTC (permalink / raw)
To: Hyunwoo Kim
Cc: deller, linux-fbdev, Masami Ichikawa, cip-dev,
Harshit Mogalapalli
On Mon, Sep 19, 2022 at 11:22:41PM -0700, Hyunwoo Kim wrote:
> On Tue, Sep 20, 2022 at 09:13:31AM +0300, Dan Carpenter wrote:
> > On Tue, Sep 20, 2022 at 09:02:34AM +0300, Dan Carpenter wrote:
> > > On Mon, Jun 20, 2022 at 07:00:10AM -0700, Hyunwoo Kim wrote:
> > > > In pxa3xx_gcu_write, a count parameter of
> > > > type size_t is passed to words of type int.
> > > > Then, copy_from_user may cause a heap overflow because
> > > > it is used as the third argument of copy_from_user.
> > > >
> > > > Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
> > > > ---
> > > > drivers/video/fbdev/pxa3xx-gcu.c | 2 +-
> > > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/video/fbdev/pxa3xx-gcu.c b/drivers/video/fbdev/pxa3xx-gcu.c
> > > > index 043cc8f9ef1c..c3cd1e1cc01b 100644
> > > > --- a/drivers/video/fbdev/pxa3xx-gcu.c
> > > > +++ b/drivers/video/fbdev/pxa3xx-gcu.c
> > > > @@ -381,7 +381,7 @@ pxa3xx_gcu_write(struct file *file, const char *buff,
> > > > struct pxa3xx_gcu_batch *buffer;
> > > > struct pxa3xx_gcu_priv *priv = to_pxa3xx_gcu_priv(file);
> > > >
> > > > - int words = count / 4;
> > > > + size_t words = count / 4;
> > >
> > > The count variable is actually capped at MAX_RW_COUNT in vfs_write()
> > > so "words" cannot be negative. This patch helps clean up the code but
> > > it does not affect run time.
> >
> > Btw, the other thing which prevents this from being expliotable is that
> > if you pass a negative value to copy_from_user() it will not copy
> > anything because of the check in check_copy_size(). See commit
> > 6d13de1489b6 ("uaccess: disallow > INT_MAX copy sizes").
> >
> > Linus has sort of gotten annoyed with me before for pointing this stuff
> > out because it seemed like maybe I wasn't properly grateful to people
> > auditing the code and fixing bugs. I am grateful. This patch is
> > totally the correct thing to do. It's just that it's not really
> > exploitable as described in the commit message.
>
> I found the code that might have the vulnerability, and submitted a patch without actually debugging it.
> This is entirely my fault. sorry.
>
> Should I submit a fix patch that fixes the commit message?
>
> Sorry again.
No no. No need to appologize or resend anything. This is just
information to help in future research.
regards,
dan carpenter
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2022-09-20 7:13 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2022-09-20 6:02 [PATCH] pxa3xx-gcu: Fix integer overflow in pxa3xx_gcu_write Dan Carpenter
2022-09-20 6:13 ` Dan Carpenter
2022-09-20 6:22 ` Hyunwoo Kim
2022-09-20 7:12 ` Dan Carpenter
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox