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BUG: KASAN: use-after-free in hpfs_bplus_lookup+0x4f4/0x880
Read of size 4 at addr ffff888039d7d004 by task syz.6.433/9448

CPU: 0 UID: 0 PID: 9448 Comm: syz.6.433 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150
 print_address_description+0x55/0x1e0
 print_report+0x58/0x70
 kasan_report+0x117/0x150
 hpfs_bplus_lookup+0x4f4/0x880
 hpfs_bmap+0x230/0x4e0
 hpfs_get_block+0xa8/0x6e0
 do_mpage_readpage+0x801/0x1980
 mpage_readahead+0x3f9/0x810
 read_pages+0x193/0x5a0
 page_cache_ra_unbounded+0x794/0xa10
 page_cache_ra_order+0xae4/0xe80
 filemap_get_pages+0x4c0/0x1ef0
 filemap_read+0x447/0x1230
 __kernel_read+0x504/0x9b0
 integrity_kernel_read+0x89/0xd0
 ima_calc_file_hash+0x446/0x860
 ima_collect_measurement+0x51d/0x9c0
 process_measurement+0x12cd/0x1c80
 ima_file_check+0xe1/0x130
 security_file_post_open+0xb3/0x260
 path_openat+0x2e4d/0x3860
 do_file_open+0x23e/0x4a0
 do_sys_openat2+0x113/0x200
 __x64_sys_openat+0x138/0x170
 do_syscall_64+0x15f/0xf80
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb69eb9cdd9
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:00007fb69f9bd028 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fb69ee15fa0 RCX: 00007fb69eb9cdd9
RDX: 0000000000088040 RSI: 0000200000000200 RDI: ffffffffffffff9c
RBP: 00007fb69ec32d69 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb69ee16038 R14: 00007fb69ee15fa0 R15: 00007ffc18c2abe8
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x7fb694874 pfn:0x39d7d
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea0000e7c748 ffffea0000e74708 0000000000000000
raw: 00000007fb694874 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 9448, tgid 9447 (syz.6.433), ts 216262657796, free_ts 216572961784
 post_alloc_hook+0x231/0x280
 get_page_from_freelist+0x24ba/0x2540
 __alloc_frozen_pages_noprof+0x18d/0x380
 alloc_pages_mpol+0x235/0x490
 folio_alloc_mpol_noprof+0x39/0x160
 vma_alloc_folio_noprof+0xe1/0x1e0
 do_pte_missing+0x159d/0x33f0
 handle_mm_fault+0x1bd7/0x3170
 do_user_addr_fault+0xa73/0x1340
 exc_page_fault+0x6a/0xc0
 asm_exc_page_fault+0x26/0x30
page last free pid 9448 tgid 9447 stack trace:
 free_unref_folios+0xcec/0x1480
 folios_put_refs+0x9ff/0xb40
 free_pages_and_swap_cache+0x2b9/0x490
 tlb_flush_mmu+0x6d3/0xa30
 tlb_finish_mmu+0xf9/0x230
 unmap_region+0x2a5/0x330
 vms_complete_munmap_vmas+0x493/0xc60
 do_vmi_align_munmap+0x3b7/0x4b0
 do_vmi_munmap+0x252/0x2d0
 __vm_munmap+0x22c/0x3d0
 __x64_sys_munmap+0x60/0x70
 do_syscall_64+0x15f/0xf80
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff888039d7cf00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888039d7cf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888039d7d000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff888039d7d080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888039d7d100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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