Re: [syzbot] [dm?] WARNING in integrity_commit

[syzbot <syzbot+94dac3c75477e184f0b0@syzkaller.appspotmail.com>]

syzbot has found a reproducer for the following issue on:

HEAD commit:    79eb6679ef6a Merge tag 'loongarch-fixes-7.4-1' of git://gi..
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=1249a44d580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1cf189394a856f11
dashboard link: https://syzkaller.appspot.com/bug?extid=94dac3c75477e184f0b0
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12adb1a1580000

AI-generated root cause summary:
In drivers/md/dm-integrity.c, journal accounting variables (including
ic->free_sectors, ic->free_section, and section counts) are initialized
exclusively within replay_journal() rather than during target allocation in
dm_integrity_ctr(). When a dm-integrity target configured in journal mode ('J')
is resumed, dm_integrity_resume() checks whether the on-disk superblock was
modified while suspended; if superblock_changed() evaluates to true, it logs an
error and jumps to skip_writes, completely bypassing replay_journal(). When the
device is subsequently suspended or receives a flush bio, integrity_commit() is
scheduled and calls pad_uncommitted(), which validates that total journal
sections match the sum of uncommitted, committed, and free sectors; because
replay_journal() was skipped, these counters remain zero, causing the invariant
check to fail and trigger the WARN_ON.

full analysis:  https://syzkaller.appspot.com/x/ai_root_cause?x=94dac3c75477e184f0b0

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+94dac3c75477e184f0b0@syzkaller.appspotmail.com

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ic->journal_sections * ic->journal_section_entries != (ic->n_uncommitted_sections + ic->n_committed_sections) * ic->journal_section_entries + ic->free_sectors
WARNING: drivers/md/dm-integrity.c:2885 at pad_uncommitted drivers/md/dm-integrity.c:2885 [inline], CPU#1: kworker/1:2/1043
WARNING: drivers/md/dm-integrity.c:2885 at integrity_commit.cold+0x6/0x75 drivers/md/dm-integrity.c:2917, CPU#1: kworker/1:2/1043
Modules linked in:
CPU: 1 UID: 0 PID: 1043 Comm: kworker/1:2 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: dm-integrity-commit integrity_commit
RIP: 0010:pad_uncommitted drivers/md/dm-integrity.c:2885 [inline]
RIP: 0010:integrity_commit.cold+0x6/0x75 drivers/md/dm-integrity.c:2917
Code: ff e9 9d 9d 63 07 48 8b 7c 24 58 e8 11 a2 23 01 e9 e7 fe ff ff 48 8b 7c 24 40 e8 02 a2 23 01 e9 21 ff ff ff e8 88 48 a9 00 90 <0f> 0b 90 41 54 8b 8c 24 d0 00 00 00 89 da 44 89 f6 41 89 d9 45 89
RSP: 0018:ffffc90005497a68 EFLAGS: 00010093
RAX: 0000000000000000 RBX: 0000000000000050 RCX: 0000000000000001
RDX: ffff88802aa08000 RSI: ffffffff81653878 RDI: 0000000000000004
RBP: 0000000000000050 R08: 0000000000000050 R09: 0000000000000000
R10: 0000000000000003 R11: 000000000000776b R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000001 R15: 1ffff92000a92f6a
FS:  0000000000000000(0000) GS:ffff8880d4573000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8bc17ba008 CR3: 000000005652c000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 process_one_work+0xac7/0x1b10 kernel/workqueue.c:3495
 process_scheduled_works kernel/workqueue.c:3578 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3659
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>