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BUG: KASAN: use-after-free in ext4_ext_binsearch fs/ext4/extents.c:840 [inline]
BUG: KASAN: use-after-free in ext4_find_extent+0xb92/0xd80 fs/ext4/extents.c:955
Read of size 4 at addr ffff88806ea7a018 by task kworker/u8:14/6429

CPU: 0 UID: 0 PID: 6429 Comm: kworker/u8:14 Not tainted 6.14.0-syzkaller-13546-g16cd1c265776 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Workqueue: writeback wb_workfn (flush-7:5)
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:408 [inline]
 print_report+0x16e/0x5b0 mm/kasan/report.c:521
 kasan_report+0x143/0x180 mm/kasan/report.c:634
 ext4_ext_binsearch fs/ext4/extents.c:840 [inline]
 ext4_find_extent+0xb92/0xd80 fs/ext4/extents.c:955
 ext4_ext_map_blocks+0x2e6/0x7d80 fs/ext4/extents.c:4205
 ext4_map_create_blocks fs/ext4/inode.c:519 [inline]
 ext4_map_blocks+0x909/0x1a70 fs/ext4/inode.c:705
 mpage_map_one_extent fs/ext4/inode.c:2223 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2276 [inline]
 ext4_do_writepages+0x221d/0x3e50 fs/ext4/inode.c:2738
 ext4_writepages+0x26f/0x450 fs/ext4/inode.c:2828
 do_writepages+0x366/0x890 mm/page-writeback.c:2656
 __writeback_single_inode+0x14f/0x10d0 fs/fs-writeback.c:1680
 writeback_sb_inodes+0x822/0x1360 fs/fs-writeback.c:1976
 wb_writeback+0x415/0xb90 fs/fs-writeback.c:2156
 wb_do_writeback fs/fs-writeback.c:2303 [inline]
 wb_workfn+0x412/0x10b0 fs/fs-writeback.c:2343
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0xac5/0x18e0 kernel/workqueue.c:3319
 worker_thread+0x870/0xd50 kernel/workqueue.c:3400
 kthread+0x7b9/0x940 kernel/kthread.c:464
 ret_from_fork+0x4d/0x80 arch/x86/kernel/process.c:153
 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:0x760 pfn:0x6ea7a
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000000000760 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 7663, tgid 7662 (syz.0.356), ts 300571958163, free_ts 308990893811
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f4/0x240 mm/page_alloc.c:1717
 prep_new_page mm/page_alloc.c:1725 [inline]
 get_page_from_freelist+0x352b/0x36c0 mm/page_alloc.c:3652
 __alloc_frozen_pages_noprof+0x211/0x5b0 mm/page_alloc.c:4934
 alloc_pages_mpol+0x339/0x690 mm/mempolicy.c:2301
 folio_alloc_mpol_noprof+0x36/0x70 mm/mempolicy.c:2320
 shmem_alloc_folio mm/shmem.c:1854 [inline]
 shmem_alloc_and_add_folio+0x490/0x1070 mm/shmem.c:1893
 shmem_get_folio_gfp+0x655/0x1800 mm/shmem.c:2533
 shmem_fault+0x223/0x5c0 mm/shmem.c:2734
 __do_fault+0x137/0x390 mm/memory.c:5098
 do_read_fault mm/memory.c:5518 [inline]
 do_fault mm/memory.c:5652 [inline]
 do_pte_missing mm/memory.c:4160 [inline]
 handle_pte_fault+0x3f0c/0x61c0 mm/memory.c:5997
 __handle_mm_fault mm/memory.c:6140 [inline]
 handle_mm_fault+0x1129/0x1bf0 mm/memory.c:6309
 faultin_page mm/gup.c:1193 [inline]
 __get_user_pages+0x1adc/0x4180 mm/gup.c:1491
 populate_vma_page_range+0x266/0x340 mm/gup.c:1929
 __mm_populate+0x27d/0x460 mm/gup.c:2032
 mm_populate include/linux/mm.h:3470 [inline]
 vm_mmap_pgoff+0x390/0x530 mm/util.c:584
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94
page last free pid 7694 tgid 7662 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1262 [inline]
 free_unref_folios+0xe0e/0x17f0 mm/page_alloc.c:2737
 folios_put_refs+0x70a/0x800 mm/swap.c:992
 folio_batch_release include/linux/pagevec.h:101 [inline]
 shmem_undo_range+0x595/0x1820 mm/shmem.c:1125
 shmem_truncate_range mm/shmem.c:1237 [inline]
 shmem_evict_inode+0x29d/0xa80 mm/shmem.c:1365
 evict+0x4fb/0x9b0 fs/inode.c:810
 __dentry_kill+0x20d/0x630 fs/dcache.c:660
 dput+0x19f/0x2b0 fs/dcache.c:902
 __fput+0x60b/0x9f0 fs/file_table.c:473
 task_work_run+0x253/0x310 kernel/task_work.c:227
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0xa11/0x27f0 kernel/exit.c:953
 do_group_exit+0x207/0x2c0 kernel/exit.c:1102
 get_signal+0x1696/0x1730 kernel/signal.c:3034
 arch_do_signal_or_restart+0x98/0x840 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0xce/0x340 kernel/entry/common.c:218
 do_syscall_64+0x100/0x230 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88806ea79f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88806ea79f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88806ea7a000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                            ^
 ffff88806ea7a080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88806ea7a100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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