divide error in do_journal_end

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 6b6446ef Linux 4.14.204
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=12ba1f32500000
kernel config: https://syzkaller.appspot.com/x/.config?x=3b2e3745f25cbc4e
dashboard link: https://syzkaller.appspot.com/bug?extid=80bb9e37333427fa5892
compiler: gcc (GCC) 10.1.0-syz 20200507
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17d5f90c500000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1136f4fa500000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+80bb9e...@syzkaller.appspotmail.com

REISERFS (device loop0): journal params: device loop0, size 8192, journal first block 10, max trans len 1024, max batch 900, max commit age 30, max trans age 30
REISERFS (device loop0): checking transaction log (loop0)
REISERFS (device loop0): Using tea hash to sort names
REISERFS (device loop0): using 3.5.x disk format
REISERFS (device loop0): Created .reiserfs_priv - reserved for xattr storage.
divide error: 0000 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 0 PID: 7972 Comm: syz-executor660 Not tainted 4.14.204-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff888098d641c0 task.stack: ffff8880b31a0000
RIP: 0010:do_journal_end+0x212e/0x4260 fs/reiserfs/journal.c:4201
RSP: 0018:ffff8880b31a7ab8 EFLAGS: 00010246
RAX: 0000000000000005 RBX: dffffc0000000000 RCX: ffff8880b3654e00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90005af1048 R08: ffffffff8b9a44c8 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: ffff8880a256f000
R13: 0000000000000001 R14: ffff888095b42ac0 R15: 0000000000001000
FS: 0000000001a54880(0000) GS:ffff8880ba400000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000006d00a0 CR3: 0000000008e6a000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
reiserfs_sync_fs+0xbb/0xd0 fs/reiserfs/super.c:78
__sync_filesystem fs/sync.c:39 [inline]
sync_filesystem fs/sync.c:67 [inline]
sync_filesystem+0x185/0x230 fs/sync.c:48
generic_shutdown_super+0x70/0x370 fs/super.c:432
kill_block_super+0x95/0xe0 fs/super.c:1161
deactivate_locked_super+0x6c/0xd0 fs/super.c:319
deactivate_super+0x7f/0xa0 fs/super.c:350
cleanup_mnt+0x186/0x2c0 fs/namespace.c:1183
task_work_run+0x11f/0x190 kernel/task_work.c:113
exit_task_work include/linux/task_work.h:22 [inline]
do_exit+0xa08/0x27f0 kernel/exit.c:865
do_group_exit+0x100/0x2e0 kernel/exit.c:962
SYSC_exit_group kernel/exit.c:973 [inline]
SyS_exit_group+0x19/0x20 kernel/exit.c:971
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x4437a8
RSP: 002b:00007ffc84d2fa88 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00000000004437a8
RDX: 0000000000000001 RSI: 000000000000003c RDI: 0000000000000001
RBP: 00000000004c3c30 R08: 00000000000000e7 R09: ffffffffffffffd0
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00000000006d6180 R14: 0000000000000000 R15: 0000000000000000
Code: 95 c2 45 84 d3 0f 85 6a 15 00 00 83 e2 07 40 38 d6 0f 9e c2 40 84 f6 40 0f 95 c6 40 84 f2 0f 85 51 15 00 00 41 8b 7c 24 14 31 d2 <48> f7 f7 48 8d 79 18 4a 8d 34 0a 48 89 f8 48 c1 e8 03 80 3c 18
RIP: do_journal_end+0x212e/0x4260 fs/reiserfs/journal.c:4201 RSP: ffff8880b31a7ab8
---[ end trace e1d67c30bf08b1c0 ]---


---
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[syzbot]

syzbot suspects this issue was fixed by commit:

commit b74d5f70523a819aac71e0eee4f4b530e69e463a
Author: Rustam Kovhaev <rkov...@gmail.com>
Date: Sun Nov 1 14:09:58 2020 +0000

reiserfs: add check for an invalid ih_entry_count

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=157a045cd00000
start commit: 6b6446ef Linux 4.14.204
git tree: linux-4.14.y

kernel config: https://syzkaller.appspot.com/x/.config?x=3b2e3745f25cbc4e
dashboard link: https://syzkaller.appspot.com/bug?extid=80bb9e37333427fa5892

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17d5f90c500000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1136f4fa500000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: reiserfs: add check for an invalid ih_entry_count

For information about bisection process see: https://goo.gl/tpsmEJ#bisection