==================================================================
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 ffff888128544d64 by task kworker/u4:4/329

CPU: 0 PID: 329 Comm: kworker/u4:4 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Workqueue: writeback wb_workfn (flush-7:2)
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_map_blocks+0x207/0x6230 fs/ext4/extents.c:4182
 ext4_map_blocks+0x988/0x1b30 fs/ext4/inode.c:676
 mpage_map_one_extent fs/ext4/inode.c:2423 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2476 [inline]
 ext4_writepages+0x123f/0x3090 fs/ext4/inode.c:2844
 do_writepages+0x473/0x6c0 mm/page-writeback.c:2388
 __writeback_single_inode+0xd5/0x9c0 fs/fs-writeback.c:1657
 writeback_sb_inodes+0xa10/0x1610 fs/fs-writeback.c:1940
 wb_writeback+0x40b/0x9d0 fs/fs-writeback.c:2116
 wb_do_writeback fs/fs-writeback.c:2263 [inline]
 wb_workfn+0x3ac/0xf30 fs/fs-writeback.c:2304
 process_one_work+0x6be/0xba0 kernel/workqueue.c:2325
 worker_thread+0xa59/0x1200 kernel/workqueue.c:2472
 kthread+0x411/0x500 kernel/kthread.c:337
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>

The buggy address belongs to the page:
page:ffffea0004a15100 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x128544
flags: 0x4000000000000000(zone=1)
raw: 4000000000000000 ffffea0004a15188 ffffea0004a155c