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Date: Tue, 30 Jan 2018 22:12:23 -0800
From: Eric Biggers <ebiggers3@...il.com>
To: syzbot
<bot+9e3011b5e961675e736b38d6fd82ad12723a3fa3@...kaller.appspotmail.com>
Cc: akpm@...ux-foundation.org, alexander.deucher@....com,
broonie@...nel.org, chris@...is-wilson.co.uk, davem@...emloft.net,
deepa.kernel@...il.com, gregkh@...uxfoundation.org,
gscrivan@...hat.com, linux-kernel@...r.kernel.org,
linux-sctp@...r.kernel.org, luc.vanoostenryck@...il.com,
lucien.xin@...il.com, mingo@...nel.org, netdev@...r.kernel.org,
nhorman@...driver.com, syzkaller-bugs@...glegroups.com,
viro@...iv.linux.org.uk, vyasevich@...il.com,
xiyou.wangcong@...il.com
Subject: Re: KASAN: use-after-free Read in refcount_inc_not_zero
On Thu, Dec 14, 2017 at 10:23:01AM -0800, syzbot wrote:
> syzkaller has found reproducer for the following crash on
> 82bcf1def3b5f1251177ad47c44f7e17af039b4b
> git://git.cmpxchg.org/linux-mmots.git/master
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached
> Raw console output is attached.
> C reproducer is attached
> syzkaller reproducer is attached. See https://goo.gl/kgGztJ
> for information about syzkaller reproducers
>
>
> ==================================================================
> BUG: KASAN: use-after-free in __read_once_size include/linux/compiler.h:183
> [inline]
> BUG: KASAN: use-after-free in atomic_read arch/x86/include/asm/atomic.h:27
> [inline]
> BUG: KASAN: use-after-free in refcount_inc_not_zero+0x16e/0x180
> lib/refcount.c:120
> Read of size 4 at addr ffff8801c51bb200 by task syzkaller711981/3156
>
> CPU: 1 PID: 3156 Comm: syzkaller711981 Not tainted 4.15.0-rc2-mm1+ #39
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
> __dump_stack lib/dump_stack.c:17 [inline]
> dump_stack+0x194/0x257 lib/dump_stack.c:53
> print_address_description+0x73/0x250 mm/kasan/report.c:252
> kasan_report_error mm/kasan/report.c:351 [inline]
> kasan_report+0x25b/0x340 mm/kasan/report.c:409
> __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:429
> __read_once_size include/linux/compiler.h:183 [inline]
> atomic_read arch/x86/include/asm/atomic.h:27 [inline]
> refcount_inc_not_zero+0x16e/0x180 lib/refcount.c:120
> refcount_inc+0x15/0x50 lib/refcount.c:153
> get_ipc_ns include/linux/ipc_namespace.h:129 [inline]
> __get_ns_from_inode ipc/mqueue.c:110 [inline]
> get_ns_from_inode ipc/mqueue.c:118 [inline]
> mqueue_evict_inode+0x137/0x9c0 ipc/mqueue.c:402
> evict+0x481/0x920 fs/inode.c:552
> iput_final fs/inode.c:1514 [inline]
> iput+0x7b9/0xaf0 fs/inode.c:1541
> dentry_unlink_inode+0x4b0/0x5e0 fs/dcache.c:376
> __dentry_kill+0x3b7/0x6d0 fs/dcache.c:573
> shrink_dentry_list+0x3c5/0xcf0 fs/dcache.c:1020
> shrink_dcache_parent+0xba/0x230 fs/dcache.c:1454
> do_one_tree+0x15/0x50 fs/dcache.c:1485
> shrink_dcache_for_umount+0xbb/0x290 fs/dcache.c:1502
> generic_shutdown_super+0xcd/0x540 fs/super.c:424
> kill_anon_super fs/super.c:987 [inline]
> kill_litter_super+0x72/0x90 fs/super.c:997
> deactivate_locked_super+0x88/0xd0 fs/super.c:312
> deactivate_super+0x141/0x1b0 fs/super.c:343
> cleanup_mnt+0xb2/0x150 fs/namespace.c:1173
> __cleanup_mnt+0x16/0x20 fs/namespace.c:1180
> task_work_run+0x199/0x270 kernel/task_work.c:113
> exit_task_work include/linux/task_work.h:22 [inline]
> do_exit+0x9bb/0x1ae0 kernel/exit.c:869
> do_group_exit+0x149/0x400 kernel/exit.c:972
> SYSC_exit_group kernel/exit.c:983 [inline]
> SyS_exit_group+0x1d/0x20 kernel/exit.c:981
> entry_SYSCALL_64_fastpath+0x1f/0x96
> RIP: 0033:0x440729
> RSP: 002b:00007ffd090ef228 EFLAGS: 00000206 ORIG_RAX: 00000000000000e7
> RAX: ffffffffffffffda RBX: 0030656c69662f2e RCX: 0000000000440729
> RDX: 0000000000440729 RSI: 0000000000000000 RDI: 0000000000000001
> RBP: 00000000006cb018 R08: 0000000000000000 R09: 00000000004002c8
> R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000401bf0
> R13: 0000000000401c80 R14: 0000000000000000 R15: 0000000000000000
>
> Allocated by task 3156:
> save_stack+0x43/0xd0 mm/kasan/kasan.c:447
> set_track mm/kasan/kasan.c:459 [inline]
> kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
> kmem_cache_alloc_trace+0x136/0x750 mm/slab.c:3614
> kmalloc include/linux/slab.h:516 [inline]
> create_ipc_ns ipc/namespace.c:45 [inline]
> copy_ipcs+0x1b3/0x520 ipc/namespace.c:96
> create_new_namespaces+0x278/0x880 kernel/nsproxy.c:87
> unshare_nsproxy_namespaces+0xae/0x1e0 kernel/nsproxy.c:206
> SYSC_unshare kernel/fork.c:2421 [inline]
> SyS_unshare+0x653/0xfa0 kernel/fork.c:2371
> entry_SYSCALL_64_fastpath+0x1f/0x96
>
> Freed by task 3156:
> save_stack+0x43/0xd0 mm/kasan/kasan.c:447
> set_track mm/kasan/kasan.c:459 [inline]
> kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
> __cache_free mm/slab.c:3492 [inline]
> kfree+0xca/0x250 mm/slab.c:3807
> free_ipc_ns ipc/namespace.c:139 [inline]
> put_ipc_ns+0x112/0x150 ipc/namespace.c:164
> free_nsproxy+0xc0/0x1f0 kernel/nsproxy.c:180
> switch_task_namespaces+0x9d/0xc0 kernel/nsproxy.c:229
> exit_task_namespaces+0x17/0x20 kernel/nsproxy.c:234
> do_exit+0x9b6/0x1ae0 kernel/exit.c:868
> do_group_exit+0x149/0x400 kernel/exit.c:972
> SYSC_exit_group kernel/exit.c:983 [inline]
> SyS_exit_group+0x1d/0x20 kernel/exit.c:981
> entry_SYSCALL_64_fastpath+0x1f/0x96
>
syzbot hasn't hit this crash since next-20171221, and it looks like it was
caused by the patch "ipc, mqueue: lazy call kern_mount_data in new namespaces"
which was dropped and replaced by "mqueue: switch to on-demand creation of
internal mount" (thanks Al!). So, invalidating this bug so that syzbot can
report crashes here again if they occur.
#syz invalid
- Eric
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