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SubjectKASAN: use-after-free Read in blkdev_get
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Hello,

syzbot found the following crash on:

HEAD commit: f5b7769eb040 Revert "debugfs: inode: debugfs_create_dir us..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=171dc837800000
kernel config: https://syzkaller.appspot.com/x/.config?x=709f8187af941e84
dashboard link: https://syzkaller.appspot.com/bug?extid=eaeb616d85c9a0afec7d
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=177f898f800000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=147eb85f800000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+eaeb616d85c9a0afec7d@syzkaller.appspotmail.com

reiserfs: using flush barriers
REISERFS warning (device loop4): sh-2022 reiserfs_fill_super: unable to
initialize journal space
REISERFS (device loop3): using ordered data mode
reiserfs: using flush barriers
==================================================================
BUG: KASAN: use-after-free in __lock_acquire+0x3888/0x5140
kernel/locking/lockdep.c:3314
Read of size 8 at addr ffff8801a78932f8 by task syz-executor927/4536

CPU: 1 PID: 4536 Comm: syz-executor927 Not tainted 4.17.0+ #100
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
__lock_acquire+0x3888/0x5140 kernel/locking/lockdep.c:3314
lock_acquire+0x1dc/0x520 kernel/locking/lockdep.c:3924
__mutex_lock_common kernel/locking/mutex.c:757 [inline]
__mutex_lock+0x16d/0x17f0 kernel/locking/mutex.c:894
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:909
blkdev_get+0x5d8/0xb30 fs/block_dev.c:1620
blkdev_get_by_dev+0x3f/0x80 fs/block_dev.c:1736
journal_init_dev fs/reiserfs/journal.c:2628 [inline]
journal_init+0xcad/0x6a20 fs/reiserfs/journal.c:2775
reiserfs_fill_super+0xd59/0x3900 fs/reiserfs/super.c:2034
mount_bdev+0x30c/0x3e0 fs/super.c:1174
get_super_block+0x34/0x40 fs/reiserfs/super.c:2605
mount_fs+0xae/0x328 fs/super.c:1277
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+0x564/0x30b0 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:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x446fda
Code: b8 08 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 1d aa fb ff c3 66 2e 0f
1f 84 00 00 00 00 00 66 90 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff
ff 0f 83 fa a9 fb ff c3 66 0f 1f 84 00 00 00 00 00
RSP: 002b:00007fffcf4ce188 EFLAGS: 00000297 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fffcf4ce1a0 RCX: 0000000000446fda
RDX: 00007fffcf4ce1a0 RSI: 0000000020000100 RDI: 00007fffcf4ce1c0
RBP: 0000000000000001 R08: 00007fffcf4ce200 R09: 000000000000000a
R10: 0000000000000000 R11: 0000000000000297 R12: 0000000000000003
R13: 0000000000000004 R14: 0000000000000000 R15: 0000000000000001

Allocated by task 4536:
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
bdev_alloc_inode+0x1b/0x40 fs/block_dev.c:727
alloc_inode+0x63/0x190 fs/inode.c:210
new_inode_pseudo+0x69/0x1a0 fs/inode.c:895
new_inode+0x1c/0x40 fs/inode.c:924
iget5_locked+0x126/0x190 fs/inode.c:1097
bdget+0xb1/0x5c0 fs/block_dev.c:868
blkdev_get_by_dev+0x24/0x80 fs/block_dev.c:1732
journal_init_dev fs/reiserfs/journal.c:2628 [inline]
journal_init+0xcad/0x6a20 fs/reiserfs/journal.c:2775
reiserfs_fill_super+0xd59/0x3900 fs/reiserfs/super.c:2034
mount_bdev+0x30c/0x3e0 fs/super.c:1174
get_super_block+0x34/0x40 fs/reiserfs/super.c:2605
mount_fs+0xae/0x328 fs/super.c:1277
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+0x564/0x30b0 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:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 2414:
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
bdev_i_callback+0x20/0x30 fs/block_dev.c:738
__rcu_reclaim kernel/rcu/rcu.h:178 [inline]
rcu_do_batch kernel/rcu/tree.c:2558 [inline]
invoke_rcu_callbacks kernel/rcu/tree.c:2818 [inline]
__rcu_process_callbacks kernel/rcu/tree.c:2785 [inline]
rcu_process_callbacks+0xe9d/0x1760 kernel/rcu/tree.c:2802
__do_softirq+0x2e0/0xaf5 kernel/softirq.c:284

The buggy address belongs to the object at ffff8801a7893280
which belongs to the cache bdev_cache of size 1352
The buggy address is located 120 bytes inside of
1352-byte region [ffff8801a7893280, ffff8801a78937c8)
The buggy address belongs to the page:
page:ffffea00069e24c0 count:1 mapcount:0 mapping:ffff8801da9874c0
index:0xffff8801a7893ffe
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffffea0006dfab08 ffffea00069e2508 ffff8801da9874c0
raw: ffff8801a7893ffe ffff8801a7893280 0000000100000002 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8801a7893180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8801a7893200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff8801a7893280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8801a7893300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8801a7893380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
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syzbot.
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