Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751909AbbKZNKN (ORCPT ); Thu, 26 Nov 2015 08:10:13 -0500 Received: from mail-wm0-f47.google.com ([74.125.82.47]:33639 "EHLO mail-wm0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750840AbbKZNKJ (ORCPT ); Thu, 26 Nov 2015 08:10:09 -0500 MIME-Version: 1.0 In-Reply-To: <56570280.5030505@hurleysoftware.com> References: <56570280.5030505@hurleysoftware.com> From: Dmitry Vyukov Date: Thu, 26 Nov 2015 14:09:48 +0100 Message-ID: Subject: Re: use-after-free in tty_check_change To: Peter Hurley Cc: Greg Kroah-Hartman , Jiri Slaby , LKML , syzkaller , Kostya Serebryany , Alexander Potapenko , Sasha Levin , Eric Dumazet Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5216 Lines: 132 On Thu, Nov 26, 2015 at 2:00 PM, Peter Hurley wrote: > Hi Dmitry, > > On 11/26/2015 05:31 AM, Dmitry Vyukov wrote: >> Hello, >> >> The following program causes a use-after-free in tty_check_change: >> >> // autogenerated by syzkaller (http://github.com/google/syzkaller) >> #include >> #include >> #include >> #include >> >> void *thr(void *arg) >> { >> int x = 0; >> ioctl((int)(long)arg, TIOCGETD, &x); >> return 0; >> } >> >> void tty() >> { >> int fd = open("/dev/ptmx", O_RDONLY|O_SYNC); >> pthread_t th; >> pthread_create(&th, 0, thr, (void*)(long)fd); >> int x = 16; >> ioctl(fd, TIOCSETD, &x); >> pthread_join(th, 0); >> } >> >> int main() >> { >> int i; >> >> for (i = 0; i < 10; i++) { >> if (fork() == 0) { >> tty(); >> return 0; >> } >> } >> return 0; >> } >> >> >> ================================================================== >> BUG: KASAN: use-after-free in tty_ioctl+0x1f06/0x2140 at addr ffff880061aa0968 >> Read of size 8 by task a.out/6241 >> ============================================================================= >> BUG kmalloc-16 (Not tainted): kasan: bad access detected >> ----------------------------------------------------------------------------- > > Thanks for the report. I think I have the patch that fixes this in > my out-queue as part of a larger patchset. > > However, the stack backtrace below and the reported eip don't correspond > to the what I think the problem is: > > >> BUG: KASAN: use-after-free in tty_ioctl+0x1f06/0x2140 at addr ffff880061aa0968 > ^^^^^^^^^^^^^^ > this offset is off the end of compilation unit for me with gcc 4.8.4 > > Could you generate a mixed listing file of drivers/tty/tty_io.c and attach > it please? The source is plain 6ffeba9607343f15303a399bc402a538800d89d9, but I use CONFIG_KASAN=y, CONFIG_KASAN_INLINE=y and gcc version 6.0.0 20151014. KASAN does affect generated code significantly. Line numbers in the report should be correct. > Regards, > Peter Hurley > >> Disabling lock debugging due to kernel taint >> INFO: Allocated in tty_ldisc_get.part.3+0x66/0x140 age=6 cpu=3 pid=6230 >> [< none >] kmem_cache_alloc_trace+0x1cf/0x220 mm/slub.c:2589 >> [< none >] tty_ldisc_get.part.3+0x66/0x140 drivers/tty/tty_ldisc.c:172 >> [< none >] tty_set_ldisc+0x83d/0xa70 drivers/tty/tty_ldisc.c:574 >> [< none >] tty_ioctl+0xb2a/0x2140 drivers/tty/tty_io.c:2865 >> [< inline >] spin_unlock include/linux/spinlock.h:347 >> [< inline >] ioctl_fionbio fs/ioctl.c:492 >> [< none >] do_vfs_ioctl+0x681/0xe40 fs/ioctl.c:572 >> [< none >] SyS_ioctl+0x8f/0xc0 fs/readdir.c:25 >> [< none >] entry_SYSCALL_64_fastpath+0x16/0x7a >> arch/x86/entry/entry_64.S:185 >> >> INFO: Freed in tty_set_ldisc+0x4c2/0xa70 age=12 cpu=3 pid=6230 >> [< none >] kfree+0x199/0x1b0 mm/slub.c:3632 >> [< inline >] tty_ldisc_restore drivers/tty/tty_ldisc.c:493 >> [< none >] tty_set_ldisc+0x4c2/0xa70 drivers/tty/tty_ldisc.c:571 >> [< none >] tty_ioctl+0xb2a/0x2140 drivers/tty/tty_io.c:2865 >> [< inline >] spin_unlock include/linux/spinlock.h:347 >> [< inline >] ioctl_fionbio fs/ioctl.c:492 >> [< none >] do_vfs_ioctl+0x681/0xe40 fs/ioctl.c:572 >> [< none >] SyS_ioctl+0x8f/0xc0 fs/readdir.c:25 >> [< none >] entry_SYSCALL_64_fastpath+0x16/0x7a >> arch/x86/entry/entry_64.S:185 >> >> INFO: Slab 0xffffea000186a800 objects=23 used=19 fp=0xffff880061aa12d0 >> flags=0x5fffc0000004080 >> INFO: Object 0xffff880061aa0968 @offset=2408 fp=0xffff880061aa0810 >> CPU: 2 PID: 6241 Comm: a.out Tainted: G B 4.4.0-rc1+ #117 >> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 >> 00000000ffffffff ffff88006db0fab8 ffffffff827450f6 ffff88003e807980 >> ffff880061aa0968 ffff880061aa0000 ffff88006db0fae8 ffffffff81629404 >> ffff88003e807980 ffffea000186a800 ffff880061aa0968 000000000000001b >> >> Call Trace: >> [] __asan_report_load8_noabort+0x3e/0x40 >> mm/kasan/report.c:280 >> [< inline >] tty_check_change drivers/tty/tty_io.c:399 >> [] tty_ioctl+0x1f06/0x2140 drivers/tty/tty_io.c:2831 >> [< inline >] spin_unlock include/linux/spinlock.h:347 >> [< inline >] ioctl_fionbio fs/ioctl.c:492 >> [] do_vfs_ioctl+0x681/0xe40 fs/ioctl.c:572 >> [] SyS_ioctl+0x8f/0xc0 fs/readdir.c:25 >> [] entry_SYSCALL_64_fastpath+0x16/0x7a >> arch/x86/entry/entry_64.S:185 >> ================================================================== >> >> >> On commit 6ffeba9607343f15303a399bc402a538800d89d9 (Nov 24). > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/