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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+0xae6/0xcc0 fs/ext4/extents.c:955
Read of size 4 at addr ffff888075a9889c by task kworker/u8:7/1163

CPU: 1 UID: 0 PID: 1163 Comm: kworker/u8:7 Not tainted 6.15.0-rc4-syzkaller-00052-g4f79eaa2ceac #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
Workqueue: writeback wb_workfn (flush-7:0)
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:408 [inline]
 print_report+0xb4/0x290 mm/kasan/report.c:521
 kasan_report+0x118/0x150 mm/kasan/report.c:634
 ext4_ext_binsearch fs/ext4/extents.c:840 [inline]
 ext4_find_extent+0xae6/0xcc0 fs/ext4/extents.c:955
 ext4_ext_map_blocks+0x26f/0x67c0 fs/ext4/extents.c:4205
 ext4_map_create_blocks fs/ext4/inode.c:520 [inline]
 ext4_map_blocks+0x807/0x1740 fs/ext4/inode.c:706
 mpage_map_one_extent fs/ext4/inode.c:2224 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2277 [inline]
 ext4_do_writepages+0x1e11/0x3e50 fs/ext4/inode.c:2739
 ext4_writepages+0x203/0x350 fs/ext4/inode.c:2829
 do_writepages+0x3ae/0x7b0 mm/page-writeback.c:2656
 __writeback_single_inode+0x145/0xff0 fs/fs-writeback.c:1680
 writeback_sb_inodes+0x6b5/0x1000 fs/fs-writeback.c:1976
 wb_writeback+0x43b/0xaf0 fs/fs-writeback.c:2156
 wb_do_writeback fs/fs-writeback.c:2303 [inline]
 wb_workfn+0x409/0xef0 fs/fs-writeback.c:2343
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0xadb/0x17a0 kernel/workqueue.c:3319
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400
 kthread+0x70e/0x8a0 kernel/kthread.c:464
 ret_from_fork+0x4b/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:0x7fc4637e7 pfn:0x75a98
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 00000007fc4637e7 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 0x140dca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO|__GFP_COMP), pid 5812, tgid 5812 (sshd), ts 81211559659, free_ts 81238517714
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1d8/0x230 mm/page_alloc.c:1718
 prep_new_page mm/page_alloc.c:1726 [inline]
 get_page_from_freelist+0x21c7/0x22a0 mm/page_alloc.c:3688
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:4970
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2301
 folio_alloc_mpol_noprof mm/mempolicy.c:2320 [inline]
 vma_alloc_folio_noprof+0xe4/0x200 mm/mempolicy.c:2355
 folio_prealloc+0x30/0x180 mm/memory.c:-1
 alloc_anon_folio mm/memory.c:4943 [inline]
 do_anonymous_page mm/memory.c:5000 [inline]
 do_pte_missing mm/memory.c:4158 [inline]
 handle_pte_fault mm/memory.c:5997 [inline]
 __handle_mm_fault+0x2b28/0x5380 mm/memory.c:6140
 handle_mm_fault+0x2d5/0x7f0 mm/memory.c:6309
 do_user_addr_fault+0xa81/0x1390 arch/x86/mm/fault.c:1337
 handle_page_fault arch/x86/mm/fault.c:1480 [inline]
 exc_page_fault+0x68/0x110 arch/x86/mm/fault.c:1538
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
page last free pid 5812 tgid 5812 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1262 [inline]
 free_unref_folios+0xb70/0x1490 mm/page_alloc.c:2782
 folios_put_refs+0x559/0x640 mm/swap.c:992
 free_pages_and_swap_cache+0x277/0x520 mm/swap_state.c:267
 __tlb_batch_free_encoded_pages mm/mmu_gather.c:136 [inline]
 tlb_batch_pages_flush mm/mmu_gather.c:149 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:397 [inline]
 tlb_flush_mmu+0x3a0/0x680 mm/mmu_gather.c:404
 tlb_finish_mmu+0xc3/0x1d0 mm/mmu_gather.c:496
 vms_clear_ptes+0x42c/0x540 mm/vma.c:1191
 vms_complete_munmap_vmas+0x206/0x8a0 mm/vma.c:1233
 do_vmi_align_munmap+0x358/0x420 mm/vma.c:1492
 do_vmi_munmap+0x253/0x2e0 mm/vma.c:1540
 __vm_munmap+0x23b/0x3d0 mm/vma.c:3013
 __do_sys_munmap mm/mmap.c:1084 [inline]
 __se_sys_munmap mm/mmap.c:1081 [inline]
 __x64_sys_munmap+0x60/0x70 mm/mmap.c:1081
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff888075a98780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888075a98800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888075a98880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                            ^
 ffff888075a98900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888075a98980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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