On Fri, Nov 9, 2018 at 4:32 AM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > On Tue, Nov 06, 2018 at 03:55:32PM -0800, Todd Kjos wrote: > > Malicious code can attempt to free buffers using the > > BC_FREE_BUFFER ioctl to binder. There are protections > > against a user freeing a buffer while in use by the > > kernel, however there was a window where BC_FREE_BUFFER > > could be used to free a recently allocated buffer that > > was not completely initialized. This resulted in a > > use-after-free detected by KASAN with a malicious > > test program. > > > > This window is closed by setting the buffer's > > allow_user_free attribute to 0 when the buffer > > is allocated or when the user has previously > > freed it instead of waiting for the caller > > to set it. The problem was that when the struct > > buffer was recycled, allow_user_free was stale > > and set to 1 allowing a free to go through. > > > > Signed-off-by: Todd Kjos <tkjos@xxxxxxxxxx> > > Acked-by: Arve Hjønnevåg <arve@xxxxxxxxxxx> > > No "stable" tag here? Any idea how far back the stable backporting > should go, if any? Sorry about that. It should be backported to 4.14 and later. > > thanks, > > greg k-h
