loop2: detected capacity change from 0 to 1024
EXT4-fs (loop2): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: none.
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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 ffff88805e548c70 by task syz.2.37/6122

CPU: 1 UID: 0 PID: 6122 Comm: syz.2.37 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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:841 [inline]
 ext4_find_extent+0xae6/0xcc0 fs/ext4/extents.c:956
 ext4_ext_map_blocks+0x29d/0x6b80 fs/ext4/extents.c:4208
 ext4_map_create_blocks fs/ext4/inode.c:613 [inline]
 ext4_map_blocks+0x8da/0x1830 fs/ext4/inode.c:816
 _ext4_get_block+0x1e3/0x470 fs/ext4/inode.c:916
 ext4_get_block_unwritten+0x2e/0x100 fs/ext4/inode.c:949
 ext4_block_write_begin+0xb14/0x1950 fs/ext4/inode.c:1203
 ext4_write_begin+0xb40/0x1870 fs/ext4/ext4_jbd2.h:-1
 ext4_da_write_begin+0x355/0xd30 fs/ext4/inode.c:3130
 generic_perform_write+0x2af/0x8b0 mm/filemap.c:4314
 ext4_buffered_write_iter+0xd0/0x3a0 fs/ext4/file.c:299
 ext4_file_write_iter+0x299/0x1c20 fs/ext4/file.c:-1
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x629/0xba0 fs/read_write.c:686
 ksys_pwrite64 fs/read_write.c:793 [inline]
 __do_sys_pwrite64 fs/read_write.c:801 [inline]
 __se_sys_pwrite64 fs/read_write.c:798 [inline]
 __x64_sys_pwrite64+0x19c/0x230 fs/read_write.c:798
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f6eb2a6acb9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f6eb0cc6028 EFLAGS: 00000246 ORIG_RAX: 0000000000000012
RAX: ffffffffffffffda RBX: 00007f6eb2ce5fa0 RCX: 00007f6eb2a6acb9
RDX: 000000000000fdef RSI: 0000200000000140 RDI: 0000000000000005
RBP: 00007f6eb2ad8bf7 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000e7c R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6eb2ce6038 R14: 00007f6eb2ce5fa0 R15: 00007ffd6b256668
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x7fb8f0c4a pfn:0x5e548
flags: 0x80000000000000(node=0|zone=1)
page_type: f0(buddy)
raw: 0080000000000000 ffffea00017da288 ffffea0000f93f88 0000000000000000
raw: 00000007fb8f0c4a 0000000000000001 00000000f0000000 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 6104, tgid 6103 (syz.4.34), ts 114641884508, free_ts 115771855380
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x228/0x280 mm/page_alloc.c:1884
 prep_new_page mm/page_alloc.c:1892 [inline]
 get_page_from_freelist+0x28bb/0x2950 mm/page_alloc.c:3945
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5240
 alloc_pages_mpol+0xd1/0x380 mm/mempolicy.c:2486
 folio_alloc_mpol_noprof mm/mempolicy.c:2505 [inline]
 vma_alloc_folio_noprof+0xea/0x290 mm/mempolicy.c:2540
 folio_prealloc+0x30/0x170 mm/memory.c:-1
 alloc_anon_folio mm/memory.c:5165 [inline]
 do_anonymous_page mm/memory.c:5222 [inline]
 do_pte_missing+0x86a/0x27a0 mm/memory.c:4399
 handle_pte_fault mm/memory.c:6273 [inline]
 __handle_mm_fault mm/memory.c:6411 [inline]
 handle_mm_fault+0xd0a/0x13c0 mm/memory.c:6580
 do_user_addr_fault+0xa73/0x1360 arch/x86/mm/fault.c:1336
 handle_page_fault arch/x86/mm/fault.c:1476 [inline]
 exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1532
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
page last free pid 6104 tgid 6103 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1433 [inline]
 free_unref_folios+0xc13/0x17f0 mm/page_alloc.c:3030
 folios_put_refs+0x56f/0x680 mm/swap.c:1002
 free_pages_and_swap_cache+0x2e7/0x5b0 mm/swap_state.c:355
 __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+0x3a6/0x680 mm/mmu_gather.c:404
 tlb_finish_mmu+0xc3/0x1d0 mm/mmu_gather.c:497
 vms_clear_ptes+0x44d/0x570 mm/vma.c:1276
 vms_complete_munmap_vmas+0x205/0x890 mm/vma.c:1318
 do_vmi_align_munmap+0x3bd/0x4d0 mm/vma.c:1577
 do_vmi_munmap+0x252/0x2d0 mm/vma.c:1625
 __vm_munmap+0x22c/0x3d0 mm/vma.c:3240
 __do_sys_munmap mm/mmap.c:1077 [inline]
 __se_sys_munmap mm/mmap.c:1074 [inline]
 __x64_sys_munmap+0x60/0x70 mm/mmap.c:1074
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88805e548b00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88805e548b80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88805e548c00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                                             ^
 ffff88805e548c80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88805e548d00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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