==================================================================
BUG: KASAN: use-after-free in ext4_ext_binsearch fs/ext4/extents.c:841 [inline]
BUG: KASAN: use-after-free in ext4_find_extent+0xae6/0xcc0 fs/ext4/extents.c:956
Read of size 4 at addr ffff8880120ede18 by task kworker/u9:1/32

CPU: 0 UID: 0 PID: 32 Comm: kworker/u9:1 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Workqueue: writeback wb_workfn (flush-7:1)
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xca/0x240 mm/kasan/report.c:482
 kasan_report+0x118/0x150 mm/kasan/report.c:595
 ext4_ext_binsearch fs/ext4/extents.c:841 [inline]
 ext4_find_extent+0xae6/0xcc0 fs/ext4/extents.c:956
 ext4_ext_map_blocks+0x288/0x6ac0 fs/ext4/extents.c:4208
 ext4_map_create_blocks fs/ext4/inode.c:609 [inline]
 ext4_map_blocks+0x860/0x1740 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+0x1f88/0x4610 fs/ext4/inode.c:2931
 ext4_writepages+0x205/0x350 fs/ext4/inode.c:3025
 do_writepages+0x32e/0x550 mm/page-writeback.c:2634
 __writeback_single_inode+0x145/0xff0 fs/fs-writeback.c:1719
 writeback_sb_inodes+0x6c7/0x1010 fs/fs-writeback.c:2015
 wb_writeback+0x43b/0xaf0 fs/fs-writeback.c:2195
 wb_do_writeback fs/fs-writeback.c:2342 [inline]
 wb_workfn+0x409/0xef0 fs/fs-writeback.c:2382
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3319
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x439/0x7d0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x15f pfn:0x120ed
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea0000483b08 ffffea0000673108 0000000000000000
raw: 000000000000015f 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Movable, gfp_mask 0x140cca(GFP_HIGHUSER_MOVABLE|__GFP_COMP), pid 6001, tgid 5990 (syz.1.18), ts 75895502299, free_ts 76749264907
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1851
 prep_new_page mm/page_alloc.c:1859 [inline]
 get_page_from_freelist+0x21e4/0x22c0 mm/page_alloc.c:3858
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5148
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2416
 folio_alloc_mpol_noprof+0x39/0x70 mm/mempolicy.c:2435
 shmem_alloc_folio mm/shmem.c:1908 [inline]
 shmem_alloc_and_add_folio+0x447/0xf60 mm/shmem.c:1947
 shmem_get_folio_gfp+0x59d/0x1660 mm/shmem.c:2597
 shmem_get_folio mm/shmem.c:2703 [inline]
 shmem_write_begin+0xf7/0x2b0 mm/shmem.c:3353
 generic_perform_write+0x2c5/0x900 mm/filemap.c:4175
 shmem_file_write_iter+0xf8/0x120 mm/shmem.c:3528
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x5c9/0xb30 fs/read_write.c:686
 ksys_write+0x145/0x250 fs/read_write.c:738
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 6001 tgid 5990 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1395 [inline]
 free_unref_folios+0xdbd/0x1520 mm/page_alloc.c:2952
 folios_put_refs+0x559/0x640 mm/swap.c:999
 folio_batch_release include/linux/pagevec.h:101 [inline]
 shmem_undo_range+0x49e/0x14b0 mm/shmem.c:1157
 shmem_truncate_range mm/shmem.c:1269 [inline]
 shmem_evict_inode+0x272/0xa70 mm/shmem.c:1397
 evict+0x504/0x9c0 fs/inode.c:810
 __dentry_kill+0x209/0x660 fs/dcache.c:669
 dput+0x19f/0x2b0 fs/dcache.c:911
 __fput+0x68e/0xa70 fs/file_table.c:476
 fput_close_sync+0x119/0x200 fs/file_table.c:573
 __do_sys_close fs/open.c:1587 [inline]
 __se_sys_close fs/open.c:1572 [inline]
 __x64_sys_close+0x7f/0x110 fs/open.c:1572
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff8880120edd00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8880120edd80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8880120ede00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                            ^
 ffff8880120ede80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8880120edf00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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