KASAN: use-after-free Read in debugfs_remove (2)

From: syzbot
Date: Mon Apr 23 2018 - 06:33:10 EST

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Hello,

syzbot hit the following crash on upstream commit
83beed7b2b26f232d782127792dd0cd4362fdc41 (Fri Apr 20 17:56:32 2018 +0000)
Merge branch 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/evalenti/linux-soc-thermal
syzbot dashboard link: https://syzkaller.appspot.com/bug?extid=db48ce201b524603190a

Unfortunately, I don't have any reproducer for this crash yet.
Raw console output: https://syzkaller.appspot.com/x/log.txt?id=4855303350779904
Kernel config: https://syzkaller.appspot.com/x/.config?id=1808800213120130118
compiler: gcc (GCC) 8.0.1 20180413 (experimental)

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+db48ce201b524603190a@xxxxxxxxxxxxxxxxxxxxxxxxx
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R13: 0000000020000080 R14: 0000000000000000 R15: 0000000000000000
QAT: Invalid ioctl
print_req_error: I/O error, dev loop199, sector 2
hfsplus: unable to find HFS+ superblock
==================================================================
BUG: KASAN: use-after-free in debugfs_remove+0x10b/0x130 fs/debugfs/inode.c:682
Read of size 8 at addr ffff8801b2be1380 by task syz-executor6/10824

CPU: 1 PID: 10824 Comm: syz-executor6 Not tainted 4.17.0-rc1+ #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1b9/0x294 lib/dump_stack.c:113
print_address_description+0x6c/0x20b mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
debugfs_remove+0x10b/0x130 fs/debugfs/inode.c:682
bdi_debug_unregister mm/backing-dev.c:127 [inline]
bdi_unregister+0x606/0x8e0 mm/backing-dev.c:934
release_bdi mm/backing-dev.c:951 [inline]
kref_put include/linux/kref.h:70 [inline]
bdi_put+0x153/0x180 mm/backing-dev.c:960
generic_shutdown_super+0x3c2/0x520 fs/super.c:457
kill_anon_super+0x3c/0x50 fs/super.c:1036
fuse_kill_sb_anon+0x90/0xb0 fs/fuse/inode.c:1205
deactivate_locked_super+0x97/0x100 fs/super.c:316
deactivate_super+0x188/0x1b0 fs/super.c:347
cleanup_mnt+0xbf/0x160 fs/namespace.c:1174
__cleanup_mnt+0x16/0x20 fs/namespace.c:1181
task_work_run+0x1e4/0x290 kernel/task_work.c:113
exit_task_work include/linux/task_work.h:22 [inline]
do_exit+0x1aee/0x2730 kernel/exit.c:865
do_group_exit+0x16f/0x430 kernel/exit.c:968
__do_sys_exit_group kernel/exit.c:979 [inline]
__se_sys_exit_group kernel/exit.c:977 [inline]
__x64_sys_exit_group+0x3e/0x50 kernel/exit.c:977
do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x455389
RSP: 002b:00007fff28940e58 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 000000000000006b RCX: 0000000000455389
RDX: 000000000040f380 RSI: 0000000000a44bd0 RDI: 0000000000000045
RBP: 00000000004b9ed5 R08: 000000000000000d R09: 0000000000000000
R10: 000000000297f940 R11: 0000000000000246 R12: 0000000002980940
R13: 0000000000000000 R14: 00000000000000fe R15: 0000000000094af1

Allocated by task 11096:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490
kmem_cache_alloc+0x12e/0x760 mm/slab.c:3554
__d_alloc+0xc0/0xd30 fs/dcache.c:1638
d_alloc+0x8e/0x370 fs/dcache.c:1722
d_alloc_parallel+0x152/0x1e80 fs/dcache.c:2497
__lookup_slow+0x1e6/0x540 fs/namei.c:1613
lookup_one_len+0x1c7/0x210 fs/namei.c:2490
start_creating+0xc6/0x200 fs/debugfs/inode.c:308
debugfs_create_dir+0x23/0x3c0 fs/debugfs/inode.c:505
bdi_debug_register mm/backing-dev.c:110 [inline]
bdi_register_va.part.10+0x318/0x970 mm/backing-dev.c:875
bdi_register_va+0x68/0x80 mm/backing-dev.c:884
super_setup_bdi_name+0x123/0x220 fs/super.c:1319
fuse_bdi_init fs/fuse/inode.c:987 [inline]
fuse_fill_super+0xe6e/0x1e20 fs/fuse/inode.c:1110
mount_nodev+0x6b/0x110 fs/super.c:1210
fuse_mount+0x2c/0x40 fs/fuse/inode.c:1192
mount_fs+0xae/0x328 fs/super.c:1267
vfs_kern_mount.part.34+0xd4/0x4d0 fs/namespace.c:1037
vfs_kern_mount fs/namespace.c:1027 [inline]
do_new_mount fs/namespace.c:2518 [inline]
do_mount+0x564/0x3070 fs/namespace.c:2848
ksys_mount+0x12d/0x140 fs/namespace.c:3064
__do_sys_mount fs/namespace.c:3078 [inline]
__se_sys_mount fs/namespace.c:3075 [inline]
__x64_sys_mount+0xbe/0x150 fs/namespace.c:3075
do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 11095:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
__kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
__cache_free mm/slab.c:3498 [inline]
kmem_cache_free+0x86/0x2d0 mm/slab.c:3756
__d_free+0x20/0x30 fs/dcache.c:257
__rcu_reclaim kernel/rcu/rcu.h:178 [inline]
rcu_do_batch kernel/rcu/tree.c:2675 [inline]
invoke_rcu_callbacks kernel/rcu/tree.c:2930 [inline]
__rcu_process_callbacks kernel/rcu/tree.c:2897 [inline]
rcu_process_callbacks+0x941/0x15f0 kernel/rcu/tree.c:2914
__do_softirq+0x2e0/0xaf5 kernel/softirq.c:285

The buggy address belongs to the object at ffff8801b2be1340
which belongs to the cache dentry(17:syz6) of size 288
The buggy address is located 64 bytes inside of
288-byte region [ffff8801b2be1340, ffff8801b2be1460)
The buggy address belongs to the page:
page:ffffea0006caf840 count:1 mapcount:0 mapping:ffff8801b2be1080 index:0xffff8801b2be1a20
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801b2be1080 ffff8801b2be1a20 0000000100000002
raw: ffffea000726f320 ffffea0007267820 ffff8801afc09cc0 ffff8801b1dfab80
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff8801b1dfab80

Memory state around the buggy address:
ffff8801b2be1280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8801b2be1300: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb

ffff8801b2be1380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

^
ffff8801b2be1400: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
ffff8801b2be1480: fc fc fc fc fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

---
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Next message: Baolin Wang: "Re: [PATCH] m68k: use read_persistent_clock64 consistently"
Previous message: Petr Mladek: "Re: [PATCH] printk: Ratelimit messages printed by console drivers"
Next in thread: Tetsuo Handa: "Re: KASAN: use-after-free Read in debugfs_remove (2)"
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