==================================================================
BUG: KASAN: use-after-free in ext4_ext_binsearch fs/ext4/extents.c:827 [inline]
BUG: KASAN: use-after-free in ext4_find_extent+0x994/0xb6c fs/ext4/extents.c:946
Read of size 4 at addr ffff0001b34a989c by task kworker/u4:4/1109

CPU: 1 PID: 1109 Comm: kworker/u4:4 Not tainted 5.15.181-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
Workqueue: writeback wb_workfn (flush-7:0)
Call trace:
 dump_backtrace+0x0/0x43c arch/arm64/kernel/stacktrace.c:152
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf8/0x160 lib/dump_stack.c:106
 print_address_description+0x78/0x30c mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0xec/0x15c mm/kasan/report.c:451
 __asan_report_load4_noabort+0x44/0x50 mm/kasan/report_generic.c:308
 ext4_ext_binsearch fs/ext4/extents.c:827 [inline]
 ext4_find_extent+0x994/0xb6c fs/ext4/extents.c:946
 ext4_ext_map_blocks+0x234/0x5628 fs/ext4/extents.c:4165
 ext4_map_blocks+0x7b8/0x167c fs/ext4/inode.c:673
 mpage_map_one_extent fs/ext4/inode.c:2408 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2461 [inline]
 ext4_writepages+0xf00/0x2c14 fs/ext4/inode.c:2829
 do_writepages+0x36c/0x578 mm/page-writeback.c:2386
 __writeback_single_inode+0x148/0x11f0 fs/fs-writeback.c:1647
 writeback_sb_inodes+0x7fc/0x1378 fs/fs-writeback.c:1930
 wb_writeback+0x3d8/0xe44 fs/fs-writeback.c:2104
 wb_do_writeback fs/fs-writeback.c:2247 [inline]
 wb_workfn+0x350/0xdd8 fs/fs-writeback.c:2288
 process_one_work+0x79c/0x1140 kernel/workqueue.c:2310
 worker_thread+0x8f4/0x101c kernel/workqueue.c:2457
 kthread+0x374/0x454 kernel/kthread.c:334
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:870

The buggy address belongs to the page:
page:00000000086ee22f refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x1f34a9
flags: 0x5ffc00000000000(node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000000000 fffffc00058d1008 fffffc00062734c8 0000000000000000
raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff0001b34a9780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff0001b34a9800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff0001b34a9880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                            ^
 ffff0001b34a9900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff0001b34a9980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
------------[ cut here ]------------
kernel BUG at fs/ext4/inode.c:2420!
Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP
Modules linked in:
CPU: 1 PID: 1109 Comm: kworker/u4:4 Tainted: G    B             5.15.181-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
Workqueue: writeback wb_workfn (flush-7:0)
pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : mpage_map_one_extent fs/ext4/inode.c:2420 [inline]
pc : mpage_map_and_submit_extent fs/ext4/inode.c:2461 [inline]
pc : ext4_writepages+0x2b2c/0x2c14 fs/ext4/inode.c:2829
lr : mpage_map_one_extent fs/ext4/inode.c:2420 [inline]
lr : mpage_map_and_submit_extent fs/ext4/inode.c:2461 [inline]
lr : ext4_writepages+0x2b2c/0x2c14 fs/ext4/inode.c:2829
sp : ffff800021366ee0
x29: ffff800021367200 x28: 0000000000000000 x27: ffff8000213675f0
x26: dfff800000000000 x25: ffff0000caf26000 x24: ffff0000dbec3478
x23: ffff0000caf26050 x22: 0000000000000000 x21: 1fffe0001b7d8694
x20: 0000000000000000 x19: 0000000000000010 x18: 0000000000000002
x17: 0000000000000000 x16: ffff8000111a3970 x15: ffff8000089ab238
x14: ffff8000089aca14 x13: ffff80000820c0e4 x12: 0000000000ff0100
x11: 0000000000000000 x10: 0000000000000000 x9 : ffff800008cc678c
x8 : ffff0000c9963680 x7 : 0000000000000000 x6 : ffff8000089a9a78
x5 : ffff0000c8712c28 x4 : 0000000000000000 x3 : ffff8000082b6e58
x2 : 0000000000000001 x1 : 0000000000000000 x0 : 0000000000000000
Call trace:
 mpage_map_one_extent fs/ext4/inode.c:2420 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2461 [inline]
 ext4_writepages+0x2b2c/0x2c14 fs/ext4/inode.c:2829
 do_writepages+0x36c/0x578 mm/page-writeback.c:2386
 __writeback_single_inode+0x148/0x11f0 fs/fs-writeback.c:1647
 writeback_sb_inodes+0x7fc/0x1378 fs/fs-writeback.c:1930
 wb_writeback+0x3d8/0xe44 fs/fs-writeback.c:2104
 wb_do_writeback fs/fs-writeback.c:2247 [inline]
 wb_workfn+0x350/0xdd8 fs/fs-writeback.c:2288
 process_one_work+0x79c/0x1140 kernel/workqueue.c:2310
 worker_thread+0x8f4/0x101c kernel/workqueue.c:2457
 kthread+0x374/0x454 kernel/kthread.c:334
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:870
Code: f94063f6 f2fbfffa 17fffe23 97dec859 (d4210000) 
---[ end trace 65b2ab22db68a75f ]---