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? thanks, greg k-h
