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:I found the code that might have the vulnerability, and submitted a patch without actually debugging it.
On Mon, Jun 20, 2022 at 07:00:10AM -0700, Hyunwoo Kim wrote:Btw, the other thing which prevents this from being expliotable is that
In pxa3xx_gcu_write, a count parameter ofThe count variable is actually capped at MAX_RW_COUNT in vfs_write()
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@...>
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
@@ -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;
so "words" cannot be negative. This patch helps clean up the code but
it does not affect run time.
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.
This is entirely my fault. sorry.
Should I submit a fix patch that fixes the commit message?
No no. No need to appologize or resend anything. This is just
information to help in future research.