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BUG: KASAN: use-after-free in ext4_ext_binsearch fs/ext4/extents.c:841 [inline]
BUG: KASAN: use-after-free in ext4_find_extent+0x8dc/0xa8c fs/ext4/extents.c:956
Read of size 4 at addr ffff000102102018 by task kworker/u8:37/8157

CPU: 0 UID: 0 PID: 8157 Comm: kworker/u8:37 Not tainted syzkaller #0 PREEMPT 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/30/2025
Workqueue: writeback wb_workfn (flush-7:6)
Call trace:
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C)
 __dump_stack+0x30/0x40 lib/dump_stack.c:94
 dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120
 print_address_description+0xa8/0x238 mm/kasan/report.c:378
 print_report+0x68/0x84 mm/kasan/report.c:482
 kasan_report+0xb0/0x110 mm/kasan/report.c:595
 __asan_report_load4_noabort+0x20/0x2c mm/kasan/report_generic.c:380
 ext4_ext_binsearch fs/ext4/extents.c:841 [inline]
 ext4_find_extent+0x8dc/0xa8c fs/ext4/extents.c:956
 ext4_ext_map_blocks+0x258/0x5494 fs/ext4/extents.c:4208
 ext4_map_create_blocks fs/ext4/inode.c:609 [inline]
 ext4_map_blocks+0x6f0/0x14a8 fs/ext4/inode.c:811
 mpage_map_one_extent fs/ext4/inode.c:2374 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2468 [inline]
 ext4_do_writepages+0x1b88/0x39b4 fs/ext4/inode.c:2931
 ext4_writepages+0x178/0x2a0 fs/ext4/inode.c:3025
 do_writepages+0x270/0x468 mm/page-writeback.c:2604
 __writeback_single_inode+0x15c/0x13e8 fs/fs-writeback.c:1719
 writeback_sb_inodes+0x55c/0xe40 fs/fs-writeback.c:2015
 wb_writeback+0x3cc/0xd70 fs/fs-writeback.c:2195
 wb_do_writeback fs/fs-writeback.c:2342 [inline]
 wb_workfn+0x338/0xdc0 fs/fs-writeback.c:2382
 process_one_work+0x7e8/0x155c kernel/workqueue.c:3263
 process_scheduled_works kernel/workqueue.c:3346 [inline]
 worker_thread+0x958/0xed8 kernel/workqueue.c:3427
 kthread+0x5fc/0x75c kernel/kthread.c:463
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x1372 pfn:0x142102
flags: 0x5ffc00000000000(node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000000001372 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff000102101f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff000102101f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff000102102000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                            ^
 ffff000102102080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff000102102100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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