[syzbot] [ext4?] kernel BUG in ext4_split_extent_at (3)

[syzbot <syzbot+99e33c5c0a4aebb2eb72@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    739a6c93cc75 Merge tag 'nfsd-6.16-1' of git://git.kernel.o..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11729b0c580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d11f52d3049c3790
dashboard link: https://syzkaller.appspot.com/bug?extid=99e33c5c0a4aebb2eb72
compiler:       Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f5a65b9fc0ed/disk-739a6c93.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3f1b70f2f048/vmlinux-739a6c93.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a8ab27807c85/bzImage-739a6c93.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+99e33c5c0a4aebb2eb72@syzkaller.appspotmail.com

------------[ cut here ]------------
kernel BUG at fs/ext4/extents.c:3206!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 10105 Comm: syz.7.991 Not tainted 6.16.0-rc2-syzkaller-00318-g739a6c93cc75 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:ext4_split_extent_at+0xf42/0xf70 fs/ext4/extents.c:3206
Code: 89 f9 80 e1 07 fe c1 38 c1 0f 8c 50 fb ff ff 4c 89 ff e8 51 f7 b4 ff e9 43 fb ff ff e8 87 79 51 ff 90 0f 0b e8 7f 79 51 ff 90 <0f> 0b e8 77 79 51 ff 90 0f 0b e8 6f 79 51 ff 90 0f 0b e8 67 79 51
RSP: 0018:ffffc90005166960 EFLAGS: 00010283
RAX: ffffffff826ee301 RBX: 0000000000000016 RCX: 0000000000080000
RDX: ffffc900213d9000 RSI: 00000000000369aa RDI: 00000000000369ab
RBP: ffffc90005166ab8 R08: 0000000000000003 R09: ffffc90005166a40
R10: dffffc0000000000 R11: fffff52000a2cd49 R12: ffff88814cbf7f00
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000030
FS:  00007fa0ec4006c0(0000) GS:ffff888125c51000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000020000000a000 CR3: 000000003489c000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 ext4_split_extent+0x23f/0x6e0 fs/ext4/extents.c:3406
 ext4_split_convert_extents fs/ext4/extents.c:3743 [inline]
 ext4_ext_handle_unwritten_extents fs/ext4/extents.c:3915 [inline]
 ext4_ext_map_blocks+0x1db2/0x6ac0 fs/ext4/extents.c:4274
 ext4_map_create_blocks fs/ext4/inode.c:609 [inline]
 ext4_map_blocks+0x931/0x18d0 fs/ext4/inode.c:813
 mpage_map_one_extent fs/ext4/inode.c:2348 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2401 [inline]
 ext4_do_writepages+0x212f/0x3f30 fs/ext4/inode.c:2863
 ext4_writepages+0x205/0x350 fs/ext4/inode.c:2953
 do_writepages+0x32e/0x550 mm/page-writeback.c:2636
 filemap_fdatawrite_wbc mm/filemap.c:386 [inline]
 __filemap_fdatawrite_range mm/filemap.c:419 [inline]
 file_write_and_wait_range+0x22c/0x330 mm/filemap.c:794
 generic_buffers_fsync_noflush+0x6c/0x180 fs/buffer.c:609
 ext4_fsync_nojournal fs/ext4/fsync.c:88 [inline]
 ext4_sync_file+0x332/0xb20 fs/ext4/fsync.c:147
 generic_write_sync include/linux/fs.h:3031 [inline]
 ext4_buffered_write_iter+0x2ca/0x3a0 fs/ext4/file.c:305
 ext4_file_write_iter+0x298/0x1bc0 fs/ext4/file.c:-1
 do_iter_readv_writev+0x56e/0x7f0 fs/read_write.c:-1
 vfs_writev+0x31a/0x960 fs/read_write.c:1057
 do_pwritev fs/read_write.c:1153 [inline]
 __do_sys_pwritev2 fs/read_write.c:1211 [inline]
 __se_sys_pwritev2+0x179/0x290 fs/read_write.c:1202
 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: 0033:0x7fa0eb58e929
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:00007fa0ec400038 EFLAGS: 00000246 ORIG_RAX: 0000000000000148
RAX: ffffffffffffffda RBX: 00007fa0eb7b6080 RCX: 00007fa0eb58e929
RDX: 0000000000000001 RSI: 0000200000000100 RDI: 0000000000000007
RBP: 00007fa0eb610b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000005412 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fa0eb7b6080 R15: 00007fffa0000688
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:ext4_split_extent_at+0xf42/0xf70 fs/ext4/extents.c:3206
Code: 89 f9 80 e1 07 fe c1 38 c1 0f 8c 50 fb ff ff 4c 89 ff e8 51 f7 b4 ff e9 43 fb ff ff e8 87 79 51 ff 90 0f 0b e8 7f 79 51 ff 90 <0f> 0b e8 77 79 51 ff 90 0f 0b e8 6f 79 51 ff 90 0f 0b e8 67 79 51
RSP: 0018:ffffc90005166960 EFLAGS: 00010283
RAX: ffffffff826ee301 RBX: 0000000000000016 RCX: 0000000000080000
RDX: ffffc900213d9000 RSI: 00000000000369aa RDI: 00000000000369ab
RBP: ffffc90005166ab8 R08: 0000000000000003 R09: ffffc90005166a40
R10: dffffc0000000000 R11: fffff52000a2cd49 R12: ffff88814cbf7f00
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000030
FS:  00007fa0ec4006c0(0000) GS:ffff888125d51000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c33fb2d CR3: 000000003489c000 CR4: 0000000000350ef0


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