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Date:   Thu, 3 Aug 2023 09:37:30 +0800
From:   Pengfei Xu <pengfei.xu@intel.com>
To:     syzbot <syzbot+5050ad0fb47527b1808a@syzkaller.appspotmail.com>
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Subject: Re: [syzbot] [ext4?] WARNING in ext4_file_write_iter
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On 2023-07-05 at 23:33:43 -0700, syzbot wrote:
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    6843306689af Merge tag 'net-6.5-rc1' of git://git.kernel.o..
> git tree:       net
> console output: https://syzkaller.appspot.com/x/log.txt?x=114522aca80000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=7ad417033279f15a
> dashboard link: https://syzkaller.appspot.com/bug?extid=5050ad0fb47527b1808a
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=102cb190a80000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17c49d90a80000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/f6adc10dbd71/disk-68433066.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/5c3fa1329201/vmlinux-68433066.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/84db3452bac5/bzImage-68433066.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+5050ad0fb47527b1808a@syzkaller.appspotmail.com
> 
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 5382 at fs/ext4/file.c:611 ext4_dio_write_iter fs/ext4/file.c:611 [inline]
> WARNING: CPU: 1 PID: 5382 at fs/ext4/file.c:611 ext4_file_write_iter+0x1470/0x1880 fs/ext4/file.c:720
> Modules linked in:
> CPU: 1 PID: 5382 Comm: syz-executor288 Not tainted 6.4.0-syzkaller-11989-g6843306689af #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
> RIP: 0010:ext4_dio_write_iter fs/ext4/file.c:611 [inline]
> RIP: 0010:ext4_file_write_iter+0x1470/0x1880 fs/ext4/file.c:720
> Code: 84 03 00 00 48 8b 04 24 31 ff 8b 40 20 89 c3 89 44 24 10 83 e3 08 89 de e8 5d 5a 5b ff 85 db 0f 85 d5 fc ff ff e8 30 5e 5b ff <0f> 0b e9 c9 fc ff ff e8 24 5e 5b ff 48 8b 4c 24 40 4c 89 fa 4c 89
> RSP: 0018:ffffc9000522fc30 EFLAGS: 00010293
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: ffff8880277a3b80 RSI: ffffffff82298140 RDI: 0000000000000005
> RBP: 0000000000000001 R08: 0000000000000005 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000001 R12: ffffffff8a832a60
> R13: 0000000000000000 R14: 0000000000000000 R15: fffffffffffffff5
> FS:  00007f154db95700(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f154db74718 CR3: 000000006bcc7000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  call_write_iter include/linux/fs.h:1871 [inline]
>  new_sync_write fs/read_write.c:491 [inline]
>  vfs_write+0x981/0xda0 fs/read_write.c:584
>  ksys_write+0x122/0x250 fs/read_write.c:637
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> RIP: 0033:0x7f154dc094f9
> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 15 00 00 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 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007f154db952f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> RAX: ffffffffffffffda RBX: 00007f154dc924f0 RCX: 00007f154dc094f9
> RDX: 0000000000248800 RSI: 0000000020000000 RDI: 0000000000000006
> RBP: 00007f154dc5f628 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 652e79726f6d656d
> R13: 656c6c616b7a7973 R14: 6465646165726874 R15: 00007f154dc924f8
>  </TASK>
> 

Above issue in dmesg is:
"WARNING: CPU: 1 PID: 5382 at fs/ext4/file.c:611 ext4_dio_write_iter fs/ext4/file.c:611 [inline]"

I found the similar behavior issue:
"WARNING: CPU: 0 PID: 182134 at fs/ext4/file.c:611 ext4_dio_write_iter fs/ext4/file.c:611 [inline]"
repro.report shows similar details.

Updated the bisect info for the above similar issue:
Bisected and the problem commit was:
"
310ee0902b8d9d0a13a5a13e94688a5863fa29c2: ext4: allow concurrent unaligned dio overwrites
"
After reverted the commit on top of v6.5-rc3, this issue was gone.

All information: https://github.com/xupengfe/syzkaller_logs/tree/main/230730_134501_ext4_file_write_iter
Reproduced code: https://github.com/xupengfe/syzkaller_logs/blob/main/230730_134501_ext4_file_write_iter/repro.c
repro.prog(syscall reproduced steps): https://github.com/xupengfe/syzkaller_logs/blob/main/230730_134501_ext4_file_write_iter/repro.prog
repro.report: https://github.com/xupengfe/syzkaller_logs/blob/main/230730_134501_ext4_file_write_iter/repro.report
Bisect log: https://github.com/xupengfe/syzkaller_logs/blob/main/230730_134501_ext4_file_write_iter/bisect_info.log
Kconfig: https://github.com/xupengfe/syzkaller_logs/blob/main/230730_134501_ext4_file_write_iter/kconfig_origin
Issue dmesg: https://github.com/xupengfe/syzkaller_logs/blob/main/230730_134501_ext4_file_write_iter/6eaae198076080886b9e7d57f4ae06fa782f90ef_dmesg.log

Best Regards,
Thanks!

> 
> ---
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.