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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 ffff88804d5a4ab8 by task syz.0.0/5319

CPU: 0 UID: 0 PID: 5319 Comm: syz.0.0 Not tainted 6.14.0-syzkaller-02665-g1e26c5e28ca5 #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
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:516 [inline]
 ext4_map_blocks+0x909/0x1a70 fs/ext4/inode.c:702
 _ext4_get_block+0x23b/0x6b0 fs/ext4/inode.c:781
 ext4_get_block_unwritten+0x2f/0x100 fs/ext4/inode.c:814
 __block_write_begin_int+0x691/0x1930 fs/buffer.c:2116
 block_page_mkwrite+0x3ad/0x520 fs/buffer.c:2617
 ext4_page_mkwrite+0x461/0x1130 fs/ext4/inode.c:6240
 do_page_mkwrite+0x15c/0x350 mm/memory.c:3256
 do_shared_fault mm/memory.c:5485 [inline]
 do_fault mm/memory.c:5547 [inline]
 do_pte_missing mm/memory.c:4059 [inline]
 handle_pte_fault mm/memory.c:5888 [inline]
 __handle_mm_fault+0x211b/0x6ef0 mm/memory.c:6031
 handle_mm_fault+0x3e5/0x8d0 mm/memory.c:6200
 do_user_addr_fault arch/x86/mm/fault.c:1388 [inline]
 handle_page_fault arch/x86/mm/fault.c:1480 [inline]
 exc_page_fault+0x2bb/0x8b0 arch/x86/mm/fault.c:1538
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
RIP: 0033:0x7fe18875690c
Code: 00 00 00 74 a0 83 f9 c0 0f 87 56 fe ff ff 62 e1 fe 28 6f 4e 01 48 29 fe 48 83 c7 3f 49 8d 0c 10 48 83 e7 c0 48 01 fe 48 29 f9 <f3> a4 62 c1 fe 28 7f 00 62 c1 fe 28 7f 48 01 c3 0f 1f 40 00 4c 8b
RSP: 002b:00007ffdc54d0cb8 EFLAGS: 00010206
RAX: 0000200000000600 RBX: 0000000000000004 RCX: 0000000000004f36
RDX: 0000000000005936 RSI: 00007fe18823dc23 RDI: 0000200000001000
RBP: 00007fe1889a7ba0 R08: 0000200000000600 R09: 0000000000000002
R10: 0000000000000000 R11: 0000000000000002 R12: 00007fe1889a5fac
R13: 00007fe1889a5fa0 R14: fffffffffffffffe R15: 00007ffdc54d0dd0
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x200000069 pfn:0x4d5a4
flags: 0x4fff00000000000(node=1|zone=1|lastcpupid=0x7ff)
raw: 04fff00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000200000069 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_COMP|__GFP_ZERO), pid 5319, tgid 5319 (syz.0.0), ts 75620172513, free_ts 76083587961
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f4/0x240 mm/page_alloc.c:1551
 prep_new_page mm/page_alloc.c:1559 [inline]
 get_page_from_freelist+0x3695/0x37e0 mm/page_alloc.c:3477
 __alloc_frozen_pages_noprof+0x2c5/0x7b0 mm/page_alloc.c:4740
 alloc_pages_mpol+0x339/0x690 mm/mempolicy.c:2301
 folio_alloc_mpol_noprof mm/mempolicy.c:2320 [inline]
 vma_alloc_folio_noprof+0x12d/0x260 mm/mempolicy.c:2355
 folio_prealloc+0x2e/0x170 mm/memory.c:-1
 alloc_anon_folio mm/memory.c:4834 [inline]
 do_anonymous_page mm/memory.c:4891 [inline]
 do_pte_missing mm/memory.c:4057 [inline]
 handle_pte_fault mm/memory.c:5888 [inline]
 __handle_mm_fault+0x32e8/0x6ef0 mm/memory.c:6031
 handle_mm_fault+0x3e5/0x8d0 mm/memory.c:6200
 do_user_addr_fault arch/x86/mm/fault.c:1337 [inline]
 handle_page_fault arch/x86/mm/fault.c:1480 [inline]
 exc_page_fault+0x45b/0x8b0 arch/x86/mm/fault.c:1538
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
page last free pid 5320 tgid 5319 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1127 [inline]
 free_unref_folios+0xe6c/0x18e0 mm/page_alloc.c:2707
 folios_put_refs+0x779/0x880 mm/swap.c:994
 free_pages_and_swap_cache+0x5cb/0x6a0 mm/swap_state.c:334
 __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:389 [inline]
 tlb_flush_mmu+0x3a9/0x690 mm/mmu_gather.c:396
 tlb_finish_mmu+0xd4/0x200 mm/mmu_gather.c:488
 vms_clear_ptes+0x431/0x540 mm/vma.c:1144
 vms_clean_up_area mm/vma.c:1156 [inline]
 __mmap_prepare mm/vma.c:2283 [inline]
 __mmap_region mm/vma.c:2449 [inline]
 mmap_region+0x118b/0x2fc0 mm/vma.c:2540
 do_mmap+0xd42/0x1420 mm/mmap.c:561
 vm_mmap_pgoff+0x2a2/0x530 mm/util.c:578
 ksys_mmap_pgoff+0x4ee/0x720 mm/mmap.c:607
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88804d5a4980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88804d5a4a00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88804d5a4a80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                        ^
 ffff88804d5a4b00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88804d5a4b80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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