[syzbot] [ext4?] kernel BUG in ext4_alloc_file_blocks

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    38fec10eb60d Linux 6.14
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14e2c804580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d09c42ff97b8ce6d
dashboard link: https://syzkaller.appspot.com/bug?extid=d14b2bea87fe2aaffa3b
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12e2c804580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16548bb0580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/cbcaba398075/disk-38fec10e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/7fb19649d944/vmlinux-38fec10e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3481a0b0218e/bzImage-38fec10e.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/47937005d435/mount_0.gz
  fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=13d1a43f980000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d14b2bea87fe2aaffa3b@xxxxxxxxxxxxxxxxxxxxxxxxx

------------[ cut here ]------------
kernel BUG at fs/ext4/extents.c:4487!
Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
CPU: 0 UID: 0 PID: 5851 Comm: syz-executor285 Not tainted 6.14.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
RIP: 0010:ext4_alloc_file_blocks+0xeb5/0xec0 fs/ext4/extents.c:4487
Code: b0 ff e9 86 f3 ff ff 44 89 e9 80 e1 07 fe c1 38 c1 0f 8c d3 f3 ff ff 4c 89 ef e8 96 16 b0 ff e9 c6 f3 ff ff e8 6c 5e 4b ff 90 <0f> 0b e8 14 ac 8a 09 0f 1f 40 00 90 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc9000409fae0 EFLAGS: 00010293
RAX: ffffffff82768104 RBX: 0000000000000000 RCX: ffff888034465a00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc9000409fca0 R08: ffffffff827673ea R09: 1ffff1100f07400a
R10: dffffc0000000000 R11: ffffed100f07400b R12: ffff8880783a02b0
R13: 0000000000000003 R14: 0000000000000011 R15: 0000004210000000
FS:  00007f6218e926c0(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055db3ed07680 CR3: 000000007c366000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 ext4_zero_range+0x48a/0xd70 fs/ext4/extents.c:4637
 ext4_fallocate+0x54a/0x1ea0 fs/ext4/extents.c:4787
 vfs_fallocate+0x623/0x7a0 fs/open.c:338
 ksys_fallocate fs/open.c:362 [inline]
 __do_sys_fallocate fs/open.c:367 [inline]
 __se_sys_fallocate fs/open.c:365 [inline]
 __x64_sys_fallocate+0xbc/0x110 fs/open.c:365
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f6218efc939
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 81 18 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f6218e92218 EFLAGS: 00000246 ORIG_RAX: 000000000000011d
RAX: ffffffffffffffda RBX: 00007f6218f836d8 RCX: 00007f6218efc939
RDX: 0000000000000002 RSI: 0000000000000010 RDI: 0000000000000004
RBP: 00007f6218f836d0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000007fff R11: 0000000000000246 R12: 00007f6218f5089c
R13: 0000200000001000 R14: 0000200000000000 R15: 0000200000000f80
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:ext4_alloc_file_blocks+0xeb5/0xec0 fs/ext4/extents.c:4487
Code: b0 ff e9 86 f3 ff ff 44 89 e9 80 e1 07 fe c1 38 c1 0f 8c d3 f3 ff ff 4c 89 ef e8 96 16 b0 ff e9 c6 f3 ff ff e8 6c 5e 4b ff 90 <0f> 0b e8 14 ac 8a 09 0f 1f 40 00 90 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc9000409fae0 EFLAGS: 00010293
RAX: ffffffff82768104 RBX: 0000000000000000 RCX: ffff888034465a00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc9000409fca0 R08: ffffffff827673ea R09: 1ffff1100f07400a
R10: dffffc0000000000 R11: ffffed100f07400b R12: ffff8880783a02b0
R13: 0000000000000003 R14: 0000000000000011 R15: 0000004210000000
FS:  00007f6218e926c0(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f6210aff000 CR3: 000000007c366000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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