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BUG: KASAN: use-after-free in ext4_ext_binsearch fs/ext4/extents.c:837 [inline]
BUG: KASAN: use-after-free in ext4_find_extent+0xbcc/0xe00 fs/ext4/extents.c:953
Read of size 4 at addr ffff88804f9ed018 by task kworker/u4:18/5110

CPU: 0 PID: 5110 Comm: kworker/u4:18 Not tainted 6.1.141-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: writeback wb_workfn (flush-7:6)
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x22e lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:316 [inline]
 print_report+0xa8/0x220 mm/kasan/report.c:427
 kasan_report+0x10b/0x140 mm/kasan/report.c:531
 ext4_ext_binsearch fs/ext4/extents.c:837 [inline]
 ext4_find_extent+0xbcc/0xe00 fs/ext4/extents.c:953
 ext4_ext_map_blocks+0x27d/0x66d0 fs/ext4/extents.c:4165
 ext4_map_blocks+0x9d1/0x1b60 fs/ext4/inode.c:679
 mpage_map_one_extent fs/ext4/inode.c:2434 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2487 [inline]
 ext4_writepages+0x1336/0x2e50 fs/ext4/inode.c:2855
 do_writepages+0x3b7/0x610 mm/page-writeback.c:2491
 __writeback_single_inode+0x156/0x1160 fs/fs-writeback.c:1612
 writeback_sb_inodes+0xad8/0x17d0 fs/fs-writeback.c:1903
 wb_writeback+0x468/0xd00 fs/fs-writeback.c:2077
 wb_do_writeback fs/fs-writeback.c:2220 [inline]
 wb_workfn+0x435/0xec0 fs/fs-writeback.c:2260
 process_one_work+0x898/0x1160 kernel/workqueue.c:2292
 worker_thread+0xaa2/0x1250 kernel/workqueue.c:2439
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>

The buggy address belongs to the physical page:
page:ffffea00013e7b40 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x4f9ed
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000000000001 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 6469, tgid 6468 (syz.4.388), ts 274310931258, free_ts 275509502983
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x173/0x1a0 mm/page_alloc.c:2532
 prep_new_page mm/page_alloc.c:2539 [inline]
 get_page_from_freelist+0x1a26/0x1ac0 mm/page_alloc.c:4328
 __alloc_pages+0x1df/0x4e0 mm/page_alloc.c:5614
 __folio_alloc+0xe/0x30 mm/page_alloc.c:5646
 vma_alloc_folio+0x4a3/0x900 mm/mempolicy.c:2243
 shmem_alloc_folio mm/shmem.c:1589 [inline]
 shmem_alloc_and_acct_folio+0x42e/0xb60 mm/shmem.c:1613
 shmem_get_folio_gfp+0x1361/0x3400 mm/shmem.c:1941
 shmem_fault+0x1be/0x7b0 mm/shmem.c:2156
 __do_fault+0x13b/0x4e0 mm/memory.c:4280
 do_read_fault mm/memory.c:4631 [inline]
 do_fault mm/memory.c:4760 [inline]
 handle_pte_fault mm/memory.c:5031 [inline]
 __handle_mm_fault mm/memory.c:5173 [inline]
 handle_mm_fault+0x28ca/0x3e70 mm/memory.c:5294
 faultin_page mm/gup.c:1026 [inline]
 __get_user_pages+0x3ff/0xeb0 mm/gup.c:1250
 populate_vma_page_range+0x214/0x2b0 mm/gup.c:1607
 __mm_populate+0x248/0x370 mm/gup.c:1721
 mm_populate include/linux/mm.h:2823 [inline]
 vm_mmap_pgoff+0x203/0x2b0 mm/util.c:525
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1459 [inline]
 free_pcp_prepare mm/page_alloc.c:1509 [inline]
 free_unref_page_prepare+0x8b4/0x9a0 mm/page_alloc.c:3384
 free_unref_page_list+0xbb/0x8e0 mm/page_alloc.c:3525
 release_pages+0x1f92/0x2200 mm/swap.c:1035
 __pagevec_release+0x6d/0xe0 mm/swap.c:1055
 pagevec_release include/linux/pagevec.h:71 [inline]
 folio_batch_release include/linux/pagevec.h:135 [inline]
 shmem_undo_range+0x75b/0x2050 mm/shmem.c:946
 shmem_truncate_range mm/shmem.c:1062 [inline]
 shmem_evict_inode+0x248/0xa40 mm/shmem.c:1171
 evict+0x485/0x870 fs/inode.c:705
 __dentry_kill+0x431/0x650 fs/dcache.c:611
 dentry_kill+0xb8/0x290 fs/dcache.c:-1
 dput+0xfa/0x1d0 fs/dcache.c:918
 __fput+0x5e0/0x920 fs/file_table.c:328
 task_work_run+0x1ca/0x250 kernel/task_work.c:203
 exit_task_work include/linux/task_work.h:39 [inline]
 do_exit+0x936/0x2400 kernel/exit.c:871
 do_group_exit+0x217/0x2d0 kernel/exit.c:1021
 get_signal+0x1272/0x1350 kernel/signal.c:2871
 arch_do_signal_or_restart+0xb0/0x1230 arch/x86/kernel/signal.c:871

Memory state around the buggy address:
 ffff88804f9ecf00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88804f9ecf80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88804f9ed000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                            ^
 ffff88804f9ed080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88804f9ed100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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