==================================================================
BUG: KASAN: use-after-free in ext4_ext_binsearch fs/ext4/extents.c:827 [inline]
BUG: KASAN: use-after-free in ext4_find_extent+0xbeb/0xe20 fs/ext4/extents.c:946
Read of size 4 at addr ffff888130fdbc8c by task syz.2.17/453

CPU: 1 PID: 453 Comm: syz.2.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:88
 dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:427 [inline]
 kasan_report+0xf1/0x140 mm/kasan/report.c:444
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:308
 ext4_ext_binsearch fs/ext4/extents.c:827 [inline]
 ext4_find_extent+0xbeb/0xe20 fs/ext4/extents.c:946
 ext4_ext_remove_space+0x2de/0x40d0 fs/ext4/extents.c:2834
 ext4_punch_hole+0x77c/0xbd0 fs/ext4/inode.c:4137
 ext4_fallocate+0x2b6/0x1de0 fs/ext4/extents.c:4771
 vfs_fallocate+0x4b4/0x590 fs/open.c:309
 madvise_remove mm/madvise.c:964 [inline]
 madvise_vma_behavior mm/madvise.c:988 [inline]
 madvise_walk_vmas mm/madvise.c:1218 [inline]
 do_madvise+0x1435/0x2420 mm/madvise.c:1396
 __do_sys_madvise mm/madvise.c:1409 [inline]
 __se_sys_madvise mm/madvise.c:1407 [inline]
 __x64_sys_madvise+0xa9/0xc0 mm/madvise.c:1407
 x64_sys_call+0x89b/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:29
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7ff035096ef9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ff034efb028 EFLAGS: 00000246 ORIG_RAX: 000000000000001c
RAX: ffffffffffffffda RBX: 00007ff035301fa0 RCX: 00007ff035096ef9
RDX: 0000000000000009 RSI: 0000000000600002 RDI: 0000200000000000
RBP: 00007ff03512bee0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff035302038 R14: 00007ff035301fa0 R15: 00007ffec200e5a8
 </TASK>

The buggy address belongs to the page:
page:ffffea0004c3f6c0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x130fdb
flags: 0x4000000000000000(zone=1)
raw: 4000000000000000 ffffea0004c3f708 ffffea0004c3f688 0000000000000000
raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner info is not present (never set?)

Memory state around the buggy address:
 ffff888130fdbb80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888130fdbc00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888130fdbc80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                      ^
 ffff888130fdbd00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888130fdbd80: 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:3189!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 453 Comm: syz.2.17 Tainted: G    B             syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:ext4_split_extent_at+0xe29/0xe50 fs/ext4/extents.c:3189
Code: ff ff 44 89 f1 80 e1 07 fe c1 38 c1 0f 8c fc fb ff ff 4c 89 f7 49 89 d7 e8 64 e4 d2 ff 4c 89 fa e9 e9 fb ff ff e8 e7 b5 93 ff <0f> 0b e8 e0 b5 93 ff 0f 0b e8 d9 b5 93 ff 0f 0b e8 d2 b5 93 ff 0f
RSP: 0018:ffffc90000aa74c0 EFLAGS: 00010293
RAX: ffffffff81d610f9 RBX: 0000000000000000 RCX: ffff888118a13b40
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000000000002a
RBP: ffffc90000aa7630 R08: 0000000000000000 R09: 0000000050000028
R10: dffffc0000000000 R11: fffffbfff0e18a4c R12: dffffc0000000000
R13: 000000000000002a R14: 0000000000000030 R15: 0000000000000000
FS:  00007ff034efb6c0(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff0350e4640 CR3: 000000011179c000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 ext4_force_split_extent_at fs/ext4/extents.c:319 [inline]
 ext4_ext_remove_space+0x652/0x40d0 fs/ext4/extents.c:2880
 ext4_punch_hole+0x77c/0xbd0 fs/ext4/inode.c:4137
 ext4_fallocate+0x2b6/0x1de0 fs/ext4/extents.c:4771
 vfs_fallocate+0x4b4/0x590 fs/open.c:309
 madvise_remove mm/madvise.c:964 [inline]
 madvise_vma_behavior mm/madvise.c:988 [inline]
 madvise_walk_vmas mm/madvise.c:1218 [inline]
 do_madvise+0x1435/0x2420 mm/madvise.c:1396
 __do_sys_madvise mm/madvise.c:1409 [inline]
 __se_sys_madvise mm/madvise.c:1407 [inline]
 __x64_sys_madvise+0xa9/0xc0 mm/madvise.c:1407
 x64_sys_call+0x89b/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:29
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7ff035096ef9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ff034efb028 EFLAGS: 00000246 ORIG_RAX: 000000000000001c
RAX: ffffffffffffffda RBX: 00007ff035301fa0 RCX: 00007ff035096ef9
RDX: 0000000000000009 RSI: 0000000000600002 RDI: 0000200000000000
RBP: 00007ff03512bee0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff035302038 R14: 00007ff035301fa0 R15: 00007ffec200e5a8
 </TASK>
Modules linked in:
---[ end trace 2244d867a56705f3 ]---
RIP: 0010:ext4_split_extent_at+0xe29/0xe50 fs/ext4/extents.c:3189
Code: ff ff 44 89 f1 80 e1 07 fe c1 38 c1 0f 8c fc fb ff ff 4c 89 f7 49 89 d7 e8 64 e4 d2 ff 4c 89 fa e9 e9 fb ff ff e8 e7 b5 93 ff <0f> 0b e8 e0 b5 93 ff 0f 0b e8 d9 b5 93 ff 0f 0b e8 d2 b5 93 ff 0f
RSP: 0018:ffffc90000aa74c0 EFLAGS: 00010293
RAX: ffffffff81d610f9 RBX: 0000000000000000 RCX: ffff888118a13b40
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000000000002a
RBP: ffffc90000aa7630 R08: 0000000000000000 R09: 0000000050000028
R10: dffffc0000000000 R11: fffffbfff0e18a4c R12: dffffc0000000000
R13: 000000000000002a R14: 0000000000000030 R15: 0000000000000000
FS:  00007ff034efb6c0(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005611dcbad078 CR3: 000000011179c000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400