KASAN: global-out-of-bounds Read in __d_lookup_rcu

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: b255e500c8dc net: documentation: build a directory structu..
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=12fc1beb400000
kernel config: https://syzkaller.appspot.com/x/.config?x=28ecefa8a6e10719
dashboard link: https://syzkaller.appspot.com/bug?extid=0baaffb04baa46b3685c
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
CC: [linux-...@vger.kernel.org linux-...@vger.kernel.org
vi...@zeniv.linux.org.uk]

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+0baaff...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: global-out-of-bounds in __read_once_size
include/linux/compiler.h:182 [inline]
BUG: KASAN: global-out-of-bounds in raw_seqcount_begin
include/linux/seqlock.h:184 [inline]
BUG: KASAN: global-out-of-bounds in __d_lookup_rcu+0x8a2/0xaa0
fs/dcache.c:2163
Read of size 4 at addr ffffffff8b0fa4d8 by task blkid/9639

PANIC: double fault, error_code: 0x0
CPU: 1 PID: 9639 Comm: blkid Not tainted 4.20.0-rc4+ #328
CPU: 0 PID: 9635 Comm: syz-executor3 Not tainted 4.20.0-rc4+ #328
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:match_held_lock+0x34/0x8d0 kernel/locking/lockdep.c:3401
Call Trace:
Code: 55 48 89 e5 41 57 41 56 4c 8d 75 d8 41 55 49 89 fd 48 83 c7 10 41 54
53 48 8d 9d 38 ff ff ff 48 c1 eb 03 48 81 ec c8 00 00 00 <48> c7 85 38 ff
ff ff b3 8a b5 41 48 c7 85 40 ff ff ff b7 ba 11 89
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x244/0x39d lib/dump_stack.c:113
RSP: 0018:ffff8881d9bfdfd0 EFLAGS: 00010082
RAX: 0000000000000000 RBX: 1ffff1103b37fbff RCX: 0000000000000000
RDX: dffffc0000000000 RSI: ffffffff8959b940 RDI: ffff8881c220e8d0
RBP: ffff8881d9bfe0c0 R08: ffff8881c220e040 R09: ffffed103b5c5b67
R10: ffffed103b5c5b67 R11: ffff8881dae2db3b R12: ffff8881c220e040
R13: ffff8881c220e8c0 R14: ffff8881d9bfe098 R15: 0000000000000000
FS: 00007fe7ed8e3700(0000) GS:ffff8881dae00000(0000) knlGS:0000000000000000
print_address_description.cold.7+0x58/0x1ff mm/kasan/report.c:256
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff8881d9bfdfc8 CR3: 0000000192cda000 CR4: 00000000001406f0
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
__asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432


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[syzbot]

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