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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 ffff8880756f3018 by task syz-executor277/5850

CPU: 0 UID: 0 PID: 5850 Comm: syz-executor277 Not tainted 6.15.0-syzkaller-12426-ge271ed52b344 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:408 [inline]
 print_report+0xd2/0x2b0 mm/kasan/report.c:521
 kasan_report+0x118/0x150 mm/kasan/report.c:634
 ext4_ext_binsearch fs/ext4/extents.c:841 [inline]
 ext4_find_extent+0xae6/0xcc0 fs/ext4/extents.c:956
 ext4_ext_map_blocks+0x288/0x6ac0 fs/ext4/extents.c:4208
 ext4_map_create_blocks fs/ext4/inode.c:609 [inline]
 ext4_map_blocks+0x931/0x18d0 fs/ext4/inode.c:813
 _ext4_get_block+0x200/0x4c0 fs/ext4/inode.c:892
 ext4_block_write_begin+0x6f8/0x14b0 fs/ext4/inode.c:1178
 ext4_write_begin+0xa4f/0x1680 fs/ext4/ext4_jbd2.h:-1
 ext4_da_write_begin+0x449/0xd20 fs/ext4/inode.c:3057
 generic_perform_write+0x2c4/0x910 mm/filemap.c:4112
 ext4_buffered_write_iter+0xce/0x3a0 fs/ext4/file.c:299
 ext4_file_write_iter+0x298/0x1bc0 fs/ext4/file.c:-1
 do_iter_readv_writev+0x56e/0x7f0 fs/read_write.c:-1
 vfs_writev+0x31a/0x960 fs/read_write.c:1057
 do_pwritev fs/read_write.c:1153 [inline]
 __do_sys_pwritev2 fs/read_write.c:1211 [inline]
 __se_sys_pwritev2+0x179/0x290 fs/read_write.c:1202
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe3fc82e049
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 b1 18 00 00 90 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fe3fc7c1208 EFLAGS: 00000246 ORIG_RAX: 0000000000000148
RAX: ffffffffffffffda RBX: 00007fe3fc8b56d8 RCX: 00007fe3fc82e049
RDX: 0000000000000001 RSI: 00002000000001c0 RDI: 0000000000000004
RBP: 00007fe3fc8b56d0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000e7b R11: 0000000000000246 R12: 00007fe3fc882614
R13: 000000000000006e R14: 0000200000000080 R15: 00007ffef60cc2b8
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x7f169a374 pfn:0x756f3
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea0001d5bc88 ffffea0001d5c908 0000000000000000
raw: 00000007f169a374 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 5813, tgid 5813 (sshd-session), ts 79886189644, free_ts 79942219609
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1704
 prep_new_page mm/page_alloc.c:1712 [inline]
 get_page_from_freelist+0x21d5/0x22b0 mm/page_alloc.c:3669
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:4959
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2419
 folio_alloc_mpol_noprof mm/mempolicy.c:2438 [inline]
 vma_alloc_folio_noprof+0xe4/0x200 mm/mempolicy.c:2473
 folio_prealloc+0x30/0x180 mm/memory.c:-1
 alloc_anon_folio mm/memory.c:5034 [inline]
 do_anonymous_page mm/memory.c:5091 [inline]
 do_pte_missing mm/memory.c:4249 [inline]
 handle_pte_fault mm/memory.c:6089 [inline]
 __handle_mm_fault+0x2c88/0x5620 mm/memory.c:6232
 handle_mm_fault+0x2d5/0x7f0 mm/memory.c:6401
 do_user_addr_fault+0xa81/0x1390 arch/x86/mm/fault.c:1336
 handle_page_fault arch/x86/mm/fault.c:1476 [inline]
 exc_page_fault+0x76/0xf0 arch/x86/mm/fault.c:1532
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
page last free pid 5813 tgid 5813 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1248 [inline]
 free_unref_folios+0xcd2/0x1570 mm/page_alloc.c:2763
 folios_put_refs+0x559/0x640 mm/swap.c:992
 free_pages_and_swap_cache+0x277/0x520 mm/swap_state.c:264
 __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:497
 vms_clear_ptes+0x42c/0x540 mm/vma.c:1231
 vms_complete_munmap_vmas+0x206/0x8a0 mm/vma.c:1273
 do_vmi_align_munmap+0x358/0x420 mm/vma.c:1532
 do_vmi_munmap+0x253/0x2e0 mm/vma.c:1580
 __vm_munmap+0x23b/0x3d0 mm/vma.c:3101
 __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+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff8880756f2f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8880756f2f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8880756f3000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                            ^
 ffff8880756f3080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8880756f3100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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