==================================================================
BUG: KASAN: use-after-free in ext4_ext_binsearch fs/ext4/extents.c:840 [inline]
BUG: KASAN: use-after-free in ext4_find_extent+0xaea/0xcc0 fs/ext4/extents.c:956
Read of size 4 at addr ffff88806587d018 by task kworker/u8:3/49

CPU: 1 UID: 0 PID: 49 Comm: kworker/u8:3 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Workqueue: ext4-rsv-conversion ext4_end_io_rsv_work
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xba/0x230 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 ext4_ext_binsearch fs/ext4/extents.c:840 [inline]
 ext4_find_extent+0xaea/0xcc0 fs/ext4/extents.c:956
 ext4_ext_map_blocks+0x283/0x58b0 fs/ext4/extents.c:4261
 ext4_map_create_blocks+0x11d/0x540 fs/ext4/inode.c:616
 ext4_map_blocks+0x7cd/0x11d0 fs/ext4/inode.c:809
 ext4_convert_unwritten_extents+0x2be/0x5f0 fs/ext4/extents.c:5029
 ext4_convert_unwritten_io_end_vec+0xff/0x170 fs/ext4/extents.c:5069
 ext4_end_io_end+0xc7/0x410 fs/ext4/page-io.c:200
 ext4_do_flush_completed_IO fs/ext4/page-io.c:291 [inline]
 ext4_end_io_rsv_work+0x26a/0x340 fs/ext4/page-io.c:306
 process_one_work kernel/workqueue.c:3276 [inline]
 process_scheduled_works+0xb6e/0x18c0 kernel/workqueue.c:3359
 worker_thread+0xa53/0xfc0 kernel/workqueue.c:3440
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
 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:0xe3 pfn:0x6587d
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 00000000000000e3 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 10199, tgid 10197 (syz.0.1010), ts 486180799453, free_ts 486856622883
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x231/0x280 mm/page_alloc.c:1889
 prep_new_page mm/page_alloc.c:1897 [inline]
 get_page_from_freelist+0x24dc/0x2580 mm/page_alloc.c:3962
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5250
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2484
 folio_alloc_mpol_noprof+0x39/0x70 mm/mempolicy.c:2503
 shmem_alloc_folio mm/shmem.c:1930 [inline]
 shmem_alloc_and_add_folio+0x445/0xf80 mm/shmem.c:1972
 shmem_get_folio_gfp+0x5a9/0x1670 mm/shmem.c:2567
 shmem_fault+0x179/0x390 mm/shmem.c:2768
 __do_fault+0x138/0x390 mm/memory.c:5364
 do_read_fault mm/memory.c:5799 [inline]
 do_fault mm/memory.c:5933 [inline]
 do_pte_missing+0x228f/0x3490 mm/memory.c:4477
 handle_pte_fault mm/memory.c:6317 [inline]
 __handle_mm_fault mm/memory.c:6455 [inline]
 handle_mm_fault+0x1bec/0x3310 mm/memory.c:6624
 faultin_page mm/gup.c:1126 [inline]
 __get_user_pages+0x165b/0x29d0 mm/gup.c:1428
 populate_vma_page_range+0x2be/0x3c0 mm/gup.c:1860
 __mm_populate+0x25f/0x390 mm/gup.c:1963
 mm_populate include/linux/mm.h:3894 [inline]
 vm_mmap_pgoff+0x3aa/0x4f0 mm/util.c:586
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
page last free pid 10210 tgid 10197 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1433 [inline]
 free_unref_folios+0xed5/0x16d0 mm/page_alloc.c:3040
 folios_put_refs+0x789/0x8d0 mm/swap.c:1002
 folio_batch_release include/linux/pagevec.h:101 [inline]
 shmem_undo_range+0x52c/0x1660 mm/shmem.c:1149
 shmem_truncate_range mm/shmem.c:1277 [inline]
 shmem_evict_inode+0x240/0x9e0 mm/shmem.c:1407
 evict+0x61e/0xb10 fs/inode.c:846
 __dentry_kill+0x1a2/0x5e0 fs/dcache.c:670
 finish_dput+0xc9/0x480 fs/dcache.c:879
 __fput+0x691/0xa70 fs/file_table.c:477
 task_work_run+0x1d9/0x270 kernel/task_work.c:233
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x70f/0x23c0 kernel/exit.c:976
 do_group_exit+0x21b/0x2d0 kernel/exit.c:1118
 get_signal+0x1284/0x1330 kernel/signal.c:3034
 arch_do_signal_or_restart+0xbc/0x830 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
 exit_to_user_mode_loop+0x86/0x480 kernel/entry/common.c:98
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
 do_syscall_64+0x32d/0xf80 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88806587cf00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88806587cf80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88806587d000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                            ^
 ffff88806587d080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88806587d100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================