Re: [syzbot] WARNING in cow_file_range_inline

[Johannes Thumshirn]

On 26.10.22 00:19, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    337a0a0b63f1 Merge tag 'net-6.1-rc3-1' of git://git.kernel..
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=1090e822880000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=1d3548a4365ba17d
> dashboard link: https://syzkaller.appspot.com/bug?extid=858534c396b0cdd291d2
> compiler:       Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16e5a422880000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16387a16880000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/c011f7e4e764/disk-337a0a0b.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/d019c4ed2ed2/vmlinux-337a0a0b.xz
> mounted in repro: https://storage.googleapis.com/syzbot-assets/be2f474580f9/mount_0.gz
> 
> The issue was bisected to:
> 
> commit caae78e032343df525b8d05c58b462827f10b2a3
> Author: Omar Sandoval <osandov@xxxxxx>
> Date:   Tue Mar 15 01:12:35 2022 +0000
> 
>     btrfs: move common inode creation code into btrfs_create_new_inode()
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=165f10ee880000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=155f10ee880000
> console output: https://syzkaller.appspot.com/x/log.txt?x=115f10ee880000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+858534c396b0cdd291d2@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: caae78e03234 ("btrfs: move common inode creation code into btrfs_create_new_inode()")
> 
> BTRFS info (device loop0): enabling ssd optimizations
> ------------[ cut here ]------------
> BTRFS: Transaction aborted (error -12)
> WARNING: CPU: 0 PID: 3604 at fs/btrfs/inode.c:454 cow_file_range_inline+0x87c/0x9a0 fs/btrfs/inode.c:454
> Modules linked in:
> CPU: 0 PID: 3604 Comm: syz-executor345 Not tainted 6.1.0-rc2-syzkaller-00061-g337a0a0b63f1 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/11/2022
> RIP: 0010:cow_file_range_inline+0x87c/0x9a0 fs/btrfs/inode.c:454
> Code: 49 8b 3e 48 c7 c6 40 f8 da 8a 89 da 31 c0 e8 dd 97 a6 06 eb 1a e8 34 9c fc fd 48 c7 c7 40 f7 da 8a 89 de 31 c0 e8 84 3a c4 fd <0f> 0b 41 b7 01 4c 8b 64 24 08 4c 8b 2c 24 45 0f b6 c7 4c 8b 7c 24
> RSP: 0018:ffffc90003d8ed00 EFLAGS: 00010246
> RAX: c935d7c7edbb6300 RBX: 00000000fffffff4 RCX: ffff888077ebba80
> RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
> RBP: ffffc90003d8ee30 R08: ffffffff816b8d3d R09: ffffed1017344f13
> R10: ffffed1017344f13 R11: 1ffff11017344f12 R12: 1ffff1100e669a5e
> R13: ffff88801d524001 R14: ffff88807334d2f0 R15: 00000000fffffff4
> FS:  0000555555892300(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000020003180 CR3: 000000001d484000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  cow_file_range+0x391/0xfa0 fs/btrfs/inode.c:1219
>  btrfs_run_delalloc_range+0xed4/0x11a0 fs/btrfs/inode.c:2229
>  writepage_delalloc+0x25e/0x540 fs/btrfs/extent_io.c:1968
>  __extent_writepage+0x5d6/0x14d0 fs/btrfs/extent_io.c:2272
>  extent_write_cache_pages+0x9e7/0x12d0 fs/btrfs/extent_io.c:3186
>  extent_writepages+0x228/0x550 fs/btrfs/extent_io.c:3308
>  do_writepages+0x3c3/0x680 mm/page-writeback.c:2469
>  filemap_fdatawrite_wbc+0x11e/0x170 mm/filemap.c:388
>  __filemap_fdatawrite_range mm/filemap.c:421 [inline]
>  filemap_fdatawrite_range+0x175/0x200 mm/filemap.c:439
>  btrfs_fdatawrite_range fs/btrfs/file.c:4140 [inline]
>  start_ordered_ops fs/btrfs/file.c:2026 [inline]
>  btrfs_sync_file+0x39e/0x1140 fs/btrfs/file.c:2102
>  generic_write_sync include/linux/fs.h:2883 [inline]
>  btrfs_do_write_iter+0xa6f/0x1370 fs/btrfs/file.c:1975
>  call_write_iter include/linux/fs.h:2191 [inline]
>  new_sync_write fs/read_write.c:491 [inline]
>  vfs_write+0x7dc/0xc50 fs/read_write.c:584
>  ksys_write+0x177/0x2a0 fs/read_write.c:637
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> RIP: 0033:0x7f4612b05f79
> Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007fff76769238 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007f4612b05f79
> RDX: 0000000000000001 RSI: 0000000020003180 RDI: 0000000000000006
> RBP: 00007fff76769260 R08: 0000000000000002 R09: 00007fff76769270
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000007
> R13: 00007f4612b4e6b8 R14: 00007fff76769280 R15: 0000000000000000
>  </TASK>

Not sure how applicable this is. The reproducer configures failslab to
fail every 16th call and then complains about -ENOMEM ¯\_(ツ)_/¯