Re: [Internet]Re: [PATCH] fbcon: Out-Of-Bounds write in sys_imageblit, add range check

On Tue, Jul 27, 2021 at 01:53:13AM +0000, tcs_kernel(腾讯云内核开发者) wrote:

yres and vyres can be controlled by user mode paramaters, and cause p->vrows to become a negative value. While this value be passed to real_y function, the ypos will be out of screen range.
This is an out-of-bounds write bug.
I think updatescrollmode is the right place to validate values supplied by a user ioctl, because only here makes --operation,and 0 is a legal value before that.

Please wrap your changelog text.

Signed-off-by: Tencent Cloud System tcs_kernel@tencent.com

That is not the name of a person :(

And the format isn't correct, so there's nothing we can do with this
patch, and the patch itself is corrupted and could not be applied :(

Also, what about checking these values earlier?  How can the value be 0
earlier and be acceptable?  Putting bounds on the user-provided values
would be much easier, right?

thanks,

greg k-h