==================================================================
BUG: KASAN: use-after-free in ext4_ext_binsearch fs/ext4/extents.c:826 [inline]
BUG: KASAN: use-after-free in ext4_find_extent+0xbeb/0xe20 fs/ext4/extents.c:945
Read of size 4 at addr ffff88812c54f950 by task syz.2.16/480

CPU: 0 PID: 480 Comm: syz.2.16 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
 __dump_stack+0x21/0x24 lib/dump_stack.c:77
 dump_stack_lvl+0x169/0x1d8 lib/dump_stack.c:118
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:435 [inline]
 kasan_report+0xe2/0x130 mm/kasan/report.c:452
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:308
 ext4_ext_binsearch fs/ext4/extents.c:826 [inline]
 ext4_find_extent+0xbeb/0xe20 fs/ext4/extents.c:945
 ext4_ext_remove_space+0x306/0x4920 fs/ext4/extents.c:2829
 ext4_punch_hole+0x6f8/0xad0 fs/ext4/inode.c:4217
 ext4_fallocate+0x271/0x1a70 fs/ext4/extents.c:4758
 vfs_fallocate+0x4b4/0x590 fs/open.c:310
 madvise_remove mm/madvise.c:880 [inline]
 madvise_vma_behavior mm/madvise.c:904 [inline]
 madvise_walk_vmas mm/madvise.c:1131 [inline]
 do_madvise+0x12cf/0x1df0 mm/madvise.c:1308
 __do_sys_madvise mm/madvise.c:1322 [inline]
 __se_sys_madvise mm/madvise.c:1320 [inline]
 __x64_sys_madvise+0xa9/0xc0 mm/madvise.c:1320
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f5b3b565929
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:00007f5b3afd6038 EFLAGS: 00000246 ORIG_RAX: 000000000000001c
RAX: ffffffffffffffda RBX: 00007f5b3b78cfa0 RCX: 00007f5b3b565929
RDX: 0000000000000009 RSI: 0000000000600002 RDI: 0000200000000000
RBP: 00007f5b3b5e7b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f5b3b78cfa0 R15: 00007ffe0af6f9a8

The buggy address belongs to the page:
page:ffffea0004b153c0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x12c54f
flags: 0x4000000000000000()
raw: 4000000000000000 ffffea0004b153c8 ffffea0004b153c8 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner info is not present (never set?)

Memory state around the buggy address:
 ffff88812c54f800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88812c54f880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88812c54f900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                                 ^
 ffff88812c54f980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88812c54fa00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
------------[ cut here ]------------
kernel BUG at fs/ext4/extents.c:3181!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 480 Comm: syz.2.16 Tainted: G    B             syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:ext4_split_extent_at+0xe6e/0xe90 fs/ext4/extents.c:3181
Code: 48 89 df 48 89 74 24 68 e8 1f 7e d3 ff 48 8b 74 24 68 e9 5a fb ff ff e8 90 8e 99 ff 0f 0b e8 89 8e 99 ff 0f 0b e8 82 8e 99 ff <0f> 0b e8 7b 8e 99 ff 0f 0b e8 74 8e 99 ff 0f 0b e8 6d 8e 99 ff 0f
RSP: 0018:ffffc900032ff4a0 EFLAGS: 00010293
RAX: ffffffff81ca171e RBX: 0000000000000000 RCX: ffff888117443b40
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000000000002a
RBP: ffffc900032ff610 R08: 0000000000000000 R09: 0000000050000028
R10: fffffbfff0d8ee48 R11: 1ffffffff0d8ee48 R12: 0000000000000000
R13: 0000000000000000 R14: 1ffff110258b0851 R15: 0000000000000000
FS:  00007f5b3afd66c0(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b3155ffff CR3: 0000000116a7f000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 ext4_force_split_extent_at fs/ext4/extents.c:318 [inline]
 ext4_ext_remove_space+0x677/0x4920 fs/ext4/extents.c:2875
 ext4_punch_hole+0x6f8/0xad0 fs/ext4/inode.c:4217
 ext4_fallocate+0x271/0x1a70 fs/ext4/extents.c:4758
 vfs_fallocate+0x4b4/0x590 fs/open.c:310
 madvise_remove mm/madvise.c:880 [inline]
 madvise_vma_behavior mm/madvise.c:904 [inline]
 madvise_walk_vmas mm/madvise.c:1131 [inline]
 do_madvise+0x12cf/0x1df0 mm/madvise.c:1308
 __do_sys_madvise mm/madvise.c:1322 [inline]
 __se_sys_madvise mm/madvise.c:1320 [inline]
 __x64_sys_madvise+0xa9/0xc0 mm/madvise.c:1320
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f5b3b565929
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:00007f5b3afd6038 EFLAGS: 00000246 ORIG_RAX: 000000000000001c
RAX: ffffffffffffffda RBX: 00007f5b3b78cfa0 RCX: 00007f5b3b565929
RDX: 0000000000000009 RSI: 0000000000600002 RDI: 0000200000000000
RBP: 00007f5b3b5e7b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f5b3b78cfa0 R15: 00007ffe0af6f9a8
Modules linked in:
---[ end trace 18cb027b7695ad65 ]---
RIP: 0010:ext4_split_extent_at+0xe6e/0xe90 fs/ext4/extents.c:3181
Code: 48 89 df 48 89 74 24 68 e8 1f 7e d3 ff 48 8b 74 24 68 e9 5a fb ff ff e8 90 8e 99 ff 0f 0b e8 89 8e 99 ff 0f 0b e8 82 8e 99 ff <0f> 0b e8 7b 8e 99 ff 0f 0b e8 74 8e 99 ff 0f 0b e8 6d 8e 99 ff 0f
RSP: 0018:ffffc900032ff4a0 EFLAGS: 00010293
RAX: ffffffff81ca171e RBX: 0000000000000000 RCX: ffff888117443b40
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000000000002a
RBP: ffffc900032ff610 R08: 0000000000000000 R09: 0000000050000028
R10: fffffbfff0d8ee48 R11: 1ffffffff0d8ee48 R12: 0000000000000000
R13: 0000000000000000 R14: 1ffff110258b0851 R15: 0000000000000000
FS:  00007f5b3afd66c0(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f1829302000 CR3: 0000000116a7f000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400