linux-kernel - Re: [syzbot] [ext4?] kernel BUG in ext4_write_inline

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Message-ID: <68df2d0d.050a0220.1696c6.0039.GAE@google.com>
Date: Thu, 02 Oct 2025 18:55:25 -0700
From: syzbot <syzbot+f3185be57d7e8dda32b8@...kaller.appspotmail.com>
To: adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org, 
	linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com, tytso@....edu
Subject: Re: [syzbot] [ext4?] kernel BUG in ext4_write_inline_data (3)

syzbot has found a reproducer for the following issue on:

HEAD commit:    7f7072574127 Merge tag 'kbuild-6.18-1' of git://git.kernel..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=135c1ee2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f9d13d0fd373120a
dashboard link: https://syzkaller.appspot.com/bug?extid=f3185be57d7e8dda32b8
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17e49334580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16758458580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/0dce8562bc0e/disk-7f707257.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f79b72b8bfa8/vmlinux-7f707257.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a0289c1875c1/bzImage-7f707257.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/3bb52035efeb/mount_0.gz
  fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=1022a85b980000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f3185be57d7e8dda32b8@...kaller.appspotmail.com

------------[ cut here ]------------
kernel BUG at fs/ext4/inline.c:240!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 7460 Comm: syz.5.349 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
RIP: 0010:ext4_write_inline_data+0x43c/0x440 fs/ext4/inline.c:240
Code: c1 38 c1 0f 8c 19 ff ff ff 48 89 df 49 89 d7 e8 fa b0 b0 ff 4c 89 fa e9 06 ff ff ff e8 2d 07 4c ff 90 0f 0b e8 25 07 4c ff 90 <0f> 0b 66 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 66 0f
RSP: 0018:ffffc9000bff7828 EFLAGS: 00010293
RAX: ffffffff82726f5b RBX: 0000000000000078 RCX: ffff888026215ac0
RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000078
RBP: ffff8880773424a2 R08: ffff8880599a2387 R09: 1ffff1100b334470
R10: dffffc0000000000 R11: ffffed100b334471 R12: 000000000000003c
R13: ffffc9000bff78e0 R14: 0000000000000000 R15: ffff888077341f48
FS:  00007f61146ab6c0(0000) GS:ffff888126380000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fdcd7e1e000 CR3: 0000000010f34000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 ext4_write_inline_data_end+0x336/0xab0 fs/ext4/inline.c:807
 generic_perform_write+0x62a/0x900 mm/filemap.c:4196
 ext4_buffered_write_iter+0xce/0x3a0 fs/ext4/file.c:299
 ext4_file_write_iter+0x298/0x1bc0 fs/ext4/file.c:-1
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x5c9/0xb30 fs/read_write.c:686
 ksys_write+0x145/0x250 fs/read_write.c:738
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f611378eec9
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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f61146ab038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f61139e5fa0 RCX: 00007f611378eec9
RDX: 0000000000000078 RSI: 0000200000000600 RDI: 0000000000000005
RBP: 00007f6113811f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f61139e6038 R14: 00007f61139e5fa0 R15: 00007fff25d44648
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:ext4_write_inline_data+0x43c/0x440 fs/ext4/inline.c:240
Code: c1 38 c1 0f 8c 19 ff ff ff 48 89 df 49 89 d7 e8 fa b0 b0 ff 4c 89 fa e9 06 ff ff ff e8 2d 07 4c ff 90 0f 0b e8 25 07 4c ff 90 <0f> 0b 66 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 66 0f
RSP: 0018:ffffc9000bff7828 EFLAGS: 00010293
RAX: ffffffff82726f5b RBX: 0000000000000078 RCX: ffff888026215ac0
RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000078
RBP: ffff8880773424a2 R08: ffff8880599a2387 R09: 1ffff1100b334470
R10: dffffc0000000000 R11: ffffed100b334471 R12: 000000000000003c
R13: ffffc9000bff78e0 R14: 0000000000000000 R15: ffff888077341f48
FS:  00007f61146ab6c0(0000) GS:ffff888126380000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007efcc67a1d58 CR3: 0000000010f34000 CR4: 0000000000350ef0


---
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.