KASAN: use-after-free Read in __locks_wake_up_blocks

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: f5ae2ea6 Fix built-in early-load Intel microcode alignment
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12c103aee00000
kernel config: https://syzkaller.appspot.com/x/.config?x=d9290aeb7e6cf1c4
dashboard link: https://syzkaller.appspot.com/bug?extid=922689db06e57b69c240
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+922689...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in __wake_up_common+0x5d7/0x610
kernel/sched/wait.c:81
Read of size 8 at addr ffff88808e074888 by task syz-executor.0/20572

CPU: 1 PID: 20572 Comm: syz-executor.0 Not tainted 5.5.0-rc6-syzkaller #0
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+0x197/0x210 lib/dump_stack.c:118
print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
__kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506
kasan_report+0x12/0x20 mm/kasan/common.c:639
__asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:135
__wake_up_common+0x5d7/0x610 kernel/sched/wait.c:81
__wake_up_common_lock+0xea/0x150 kernel/sched/wait.c:123
__wake_up+0xe/0x10 kernel/sched/wait.c:142
__locks_wake_up_blocks+0x120/0x180 fs/locks.c:742
locks_delete_block+0x73/0xf0 fs/locks.c:773
flock_lock_inode_wait fs/locks.c:2143 [inline]
locks_lock_inode_wait+0x16b/0x3f0 fs/locks.c:2162
locks_lock_file_wait include/linux/fs.h:1328 [inline]
__do_sys_flock fs/locks.c:2225 [inline]
__se_sys_flock fs/locks.c:2188 [inline]
__x64_sys_flock+0x30c/0x370 fs/locks.c:2188
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45aff9
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
ff 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fb6469d4c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000049
RAX: ffffffffffffffda RBX: 00007fb6469d56d4 RCX: 000000000045aff9
RDX: 0000000000000000 RSI: 0000000000000002 RDI: 0000000000000004
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000000c6 R14: 00000000004c1bff R15: 000000000075bf2c

Allocated by task 20575:
save_stack+0x23/0x90 mm/kasan/common.c:72
set_track mm/kasan/common.c:80 [inline]
__kasan_kmalloc mm/kasan/common.c:513 [inline]
__kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:486
kasan_slab_alloc+0xf/0x20 mm/kasan/common.c:521
slab_post_alloc_hook mm/slab.h:584 [inline]
slab_alloc mm/slab.c:3320 [inline]
kmem_cache_alloc+0x121/0x710 mm/slab.c:3484
kmem_cache_zalloc include/linux/slab.h:660 [inline]
locks_alloc_lock+0x1d/0x1d0 fs/locks.c:346
flock_make_lock+0x241/0x2b0 fs/locks.c:487
__do_sys_flock fs/locks.c:2207 [inline]
__se_sys_flock fs/locks.c:2188 [inline]
__x64_sys_flock+0xd5/0x370 fs/locks.c:2188
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 20575:
save_stack+0x23/0x90 mm/kasan/common.c:72
set_track mm/kasan/common.c:80 [inline]
kasan_set_free_info mm/kasan/common.c:335 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/common.c:474
kasan_slab_free+0xe/0x10 mm/kasan/common.c:483
__cache_free mm/slab.c:3426 [inline]
kmem_cache_free+0x86/0x320 mm/slab.c:3694
locks_free_lock fs/locks.c:383 [inline]
__do_sys_flock fs/locks.c:2228 [inline]
__se_sys_flock fs/locks.c:2188 [inline]
__x64_sys_flock+0x23b/0x370 fs/locks.c:2188
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff88808e0747f0
which belongs to the cache file_lock_cache of size 264
The buggy address is located 152 bytes inside of
264-byte region [ffff88808e0747f0, ffff88808e0748f8)
The buggy address belongs to the page:
page:ffffea0002381d00 refcount:1 mapcount:0 mapping:ffff8880a9932700
index:0xffff88808e074a80
raw: 00fffe0000000200 ffffea00025f86c8 ffffea0002585ac8 ffff8880a9932700
raw: ffff88808e074a80 ffff88808e074040 000000010000000a 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88808e074780: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fb fb
ffff88808e074800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff88808e074880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc
^
ffff88808e074900: fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb fb
ffff88808e074980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.