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Message-ID: <CACT4Y+Z=9ES3g+CxLErxTOjMz8r6w_YC59UZN2c+yNAVrNMwNQ@mail.gmail.com>
Date: Thu, 26 Nov 2015 14:34:53 +0100
From: Dmitry Vyukov <dvyukov@...gle.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Jiri Slaby <jslaby@...e.com>,
LKML <linux-kernel@...r.kernel.org>
Cc: Kostya Serebryany <kcc@...gle.com>,
Alexander Potapenko <glider@...gle.com>,
Eric Dumazet <edumazet@...gle.com>,
Sasha Levin <sasha.levin@...cle.com>,
Peter Hurley <peter@...leysoftware.com>
Subject: use-after-free in n_tty_read
Hello,
I've hit the following report once after booting a VM and then scp a
file into it. It is not reproducible. But maybe the stacks will give
you some hint as to how it could happen:
==================================================================
BUG: KASAN: use-after-free in n_tty_read+0x1d53/0x1e60 at addr ffff880061ec3ae0
Read of size 8 by task sshd/5796
=============================================================================
BUG kmalloc-16 (Not tainted): kasan: bad access detected
-----------------------------------------------------------------------------
Disabling lock debugging due to kernel taint
INFO: Allocated in tty_ldisc_get.part.3+0x61/0x130 age=11 cpu=3 pid=5796
[< none >] ___slab_alloc+0x489/0x4e0 mm/slub.c:2438
[< none >] __slab_alloc+0x4c/0x90 mm/slub.c:2467
[< inline >] slab_alloc_node mm/slub.c:2530
[< inline >] slab_alloc mm/slub.c:2572
[< none >] kmem_cache_alloc_trace+0x1c6/0x210 mm/slub.c:2589
[< inline >] kmalloc include/linux/slab.h:458
[< none >] tty_ldisc_get.part.3+0x61/0x130 drivers/tty/tty_ldisc.c:171
[< inline >] tty_ldisc_get drivers/tty/tty_ldisc.c:801
[< none >] tty_ldisc_init+0x13/0x70 drivers/tty/tty_ldisc.c:802
[< none >] alloc_tty_struct+0x103/0x810 drivers/tty/tty_io.c:3115
[< none >] pty_common_install+0x1a2/0x940 drivers/tty/pty.c:399
[< none >] pty_unix98_install+0xb/0x10 drivers/tty/pty.c:674
[< inline >] tty_driver_install_tty drivers/tty/tty_io.c:1430
[< none >] tty_init_dev+0xdb/0x3e0 drivers/tty/tty_io.c:1529
[< none >] ptmx_open+0xbc/0x2c0 drivers/tty/pty.c:762
[< none >] chrdev_open+0x1ef/0x570 fs/char_dev.c:388
[< none >] do_dentry_open+0x5d2/0xab0 fs/open.c:736
[< none >] vfs_open+0x166/0x1e0 fs/open.c:853
[< inline >] do_last fs/namei.c:3192
[< none >] path_openat+0xa5c/0x5e00 fs/namei.c:3324
[< none >] do_filp_open+0x170/0x230 fs/namei.c:3359
[< none >] do_sys_open+0x180/0x360 fs/open.c:1025
INFO: Freed in tty_ldisc_reinit+0xc8/0x1b0 age=7 cpu=0 pid=5798
[< none >] __slab_free+0x206/0x360 mm/slub.c:2648 (discriminator 1)
[< inline >] slab_free mm/slub.c:2803
[< none >] kfree+0x1a2/0x1c0 mm/slub.c:3632
[< inline >] tty_ldisc_put drivers/tty/tty_ldisc.c:194
[< none >] tty_ldisc_reinit+0xc8/0x1b0 drivers/tty/tty_ldisc.c:635
[< none >] tty_ldisc_hangup+0x1fa/0x5f0 drivers/tty/tty_ldisc.c:708
[< none >] __tty_hangup+0x423/0xad0 drivers/tty/tty_io.c:729
[< inline >] tty_vhangup drivers/tty/tty_io.c:802
[< none >] tty_vhangup_self+0x1c/0x40 drivers/tty/tty_io.c:820
[< none >] sys_vhangup+0x1e/0x30 fs/open.c:1121
[< none >] entry_SYSCALL_64_fastpath+0x16/0x7a
arch/x86/entry/entry_64.S:185
INFO: Slab 0xffffea000187b080 objects=23 used=16 fp=0xffff880061ec3ae0
flags=0x5fffc0000004080
INFO: Object 0xffff880061ec3ae0 @offset=6880 fp=0xffff880061ec3580
Bytes b4 ffff880061ec3ad0: f1 c1 fb ff 00 00 00 00 5a 5a 5a 5a 5a 5a
5a 5a ........ZZZZZZZZ
Object ffff880061ec3ae0: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
a5 kkkkkkkkkkkkkkk.
Redzone ffff880061ec3af0: bb bb bb bb bb bb bb bb
........
Padding ffff880061ec3c30: 5a 5a 5a 5a 5a 5a 5a 5a
ZZZZZZZZ
CPU: 3 PID: 5796 Comm: sshd Tainted: G B 4.4.0-rc2+ #51
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
ffff880061ec2000 ffff88006a377928 ffffffff826c8be0 ffff88003e807980
ffff88006a377958 ffffffff815f1604 ffff88003e807980 ffffea000187b080
ffff880061ec3ae0 ffff8800620c4670 ffff88006a377980 ffffffff815f775f
Call Trace:
[< inline >] __dump_stack lib/dump_stack.c:15
[<ffffffff826c8be0>] dump_stack+0x44/0x64 lib/dump_stack.c:50
[<ffffffff815f1604>] print_trailer+0xf4/0x150 mm/slub.c:652
[<ffffffff815f775f>] object_err+0x2f/0x40 mm/slub.c:659
[< inline >] print_address_description mm/kasan/report.c:138
[<ffffffff815f9ee0>] kasan_report_error+0x210/0x520 mm/kasan/report.c:236
[< inline >] kasan_report mm/kasan/report.c:259
[<ffffffff815fa2ee>] __asan_report_load8_noabort+0x3e/0x40
mm/kasan/report.c:280
[< inline >] n_tty_check_unthrottle drivers/tty/n_tty.c:262
[<ffffffff829e73b3>] n_tty_read+0x1d53/0x1e60 drivers/tty/n_tty.c:2302
[<ffffffff829d8596>] tty_read+0x146/0x230 drivers/tty/tty_io.c:1071
[<ffffffff81633bcb>] __vfs_read+0xdb/0x490 fs/read_write.c:432
[<ffffffff81635edb>] vfs_read+0xdb/0x2d0 fs/read_write.c:454
[< inline >] SYSC_read fs/read_write.c:569
[<ffffffff81638c1c>] SyS_read+0x10c/0x220 fs/read_write.c:562
[<ffffffff852a7876>] entry_SYSCALL_64_fastpath+0x16/0x7a
arch/x86/entry/entry_64.S:185
==================================================================
On commit 6ffeba9607343f15303a399bc402a538800d89d9.
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