On Tue, Dec 19, 2017 at 09:41:39AM +0100, Dmitry Vyukov wrote: > On Tue, Dec 19, 2017 at 9:37 AM, Tobin C. Harding <me@xxxxxxxx> wrote: > >> > <penguin-kernel@xxxxxxxxxxxxxxxxxxx> wrote: > >> >> On 2017/12/18 22:40, syzbot wrote: > >> >>> Hello, > >> >>> > >> >>> syzkaller hit the following crash on 6084b576dca2e898f5c101baef151f7bfdbb606d > >> >>> git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master > >> >>> compiler: gcc (GCC) 7.1.1 20170620 > >> >>> .config is attached > >> >>> Raw console output is attached. > >> >>> > >> >>> Unfortunately, I don't have any reproducer for this bug yet. > >> >>> > >> >>> > >> >> > >> >> This BUG is reporting > >> >> > >> >> [ 26.089789] usercopy: kernel memory overwrite attempt detected to 0000000022a5b430 (kmalloc-1024) (1024 bytes) > >> >> > >> >> line. But isn't 0000000022a5b430 strange for kmalloc(1024, GFP_KERNEL)ed kernel address? > >> > > >> > The address is hashed (see the %p threads for 4.15). > >> > >> > >> +Tobin, is there a way to disable hashing entirely? The only > >> designation of syzbot is providing crash reports to kernel developers > >> with as much info as possible. It's fine for it to leak whatever. > > > > We have new specifier %px to print addresses in hex if leaking info is > > not a worry. > > This is not a per-printf-site thing. It's per-machine thing. There is no way to disable the hashing currently built into the system. Tobin -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
