sysv_free_block: flc_count > flc_size
sysv_free_block: flc_count > flc_size
sysv_free_block: flc_count > flc_size
==================================================================
BUG: KASAN: use-after-free in sysv_new_block+0x7a7/0xa50 fs/sysv/balloc.c:113
Read of size 4 at addr ffff8880402000c8 by task syz-executor.0/5482

CPU: 2 PID: 5482 Comm: syz-executor.0 Not tainted 6.10.0-rc4-syzkaller-00148-g50736169ecc8 #0
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 lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:114
 print_address_description mm/kasan/report.c:377 [inline]
 print_report+0xc3/0x620 mm/kasan/report.c:488
 kasan_report+0xd9/0x110 mm/kasan/report.c:601
 sysv_new_block+0x7a7/0xa50 fs/sysv/balloc.c:113
 alloc_branch fs/sysv/itree.c:135 [inline]
 get_block+0x261/0x1570 fs/sysv/itree.c:254
 __block_write_begin_int+0x4fb/0x16e0 fs/buffer.c:2128
 __block_write_begin fs/buffer.c:2177 [inline]
 block_write_begin+0xb1/0x4a0 fs/buffer.c:2236
 sysv_write_begin+0x31/0xe0 fs/sysv/itree.c:490
 generic_perform_write+0x272/0x620 mm/filemap.c:4015
 __generic_file_write_iter+0x1fd/0x240 mm/filemap.c:4110
 generic_file_write_iter+0xe7/0x350 mm/filemap.c:4136
 new_sync_write fs/read_write.c:497 [inline]
 vfs_write+0x6b6/0x1140 fs/read_write.c:590
 ksys_write+0x12f/0x260 fs/read_write.c:643
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb9f287dda9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 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:00007fb9f360c0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fb9f29abf80 RCX: 00007fb9f287dda9
RDX: 00000000fffffe45 RSI: 00000000200000c0 RDI: 0000000000000004
RBP: 00007fb9f28ca47a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007fb9f29abf80 R15: 00007ffd653882a8
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xc00347d pfn:0x40200
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffff7f(buddy)
raw: 00fff00000000000 ffff88807ffd7c78 ffff88807ffd7c78 0000000000000000
raw: 000000000c00347d 0000000000000009 00000000ffffff7f 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 5192, tgid 5184 (syz-fuzzer), ts 55949393356, free_ts 58489047090
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x2d1/0x350 mm/page_alloc.c:1468
 prep_new_page mm/page_alloc.c:1476 [inline]
 get_page_from_freelist+0x136a/0x2e50 mm/page_alloc.c:3420
 __alloc_pages_noprof+0x22b/0x2460 mm/page_alloc.c:4678
 alloc_pages_mpol_noprof+0x275/0x610 mm/mempolicy.c:2265
 vma_alloc_folio_noprof+0xad/0x1f0 mm/mempolicy.c:2304
 folio_prealloc mm/memory.c:1048 [inline]
 alloc_anon_folio mm/memory.c:4397 [inline]
 do_anonymous_page mm/memory.c:4455 [inline]
 do_pte_missing mm/memory.c:3895 [inline]
 handle_pte_fault mm/memory.c:5380 [inline]
 __handle_mm_fault+0x2cc7/0x5410 mm/memory.c:5523
 handle_mm_fault+0x476/0xa00 mm/memory.c:5688
 do_user_addr_fault+0x426/0xe50 arch/x86/mm/fault.c:1338
 handle_page_fault arch/x86/mm/fault.c:1481 [inline]
 exc_page_fault+0x5c/0xc0 arch/x86/mm/fault.c:1539
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
page last free pid 5188 tgid 5184 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1088 [inline]
 free_unref_folios+0x991/0x1310 mm/page_alloc.c:2632
 folios_put_refs+0x487/0x6d0 mm/swap.c:1024
 free_pages_and_swap_cache+0x36d/0x510 mm/swap_state.c:329
 __tlb_batch_free_encoded_pages+0xf9/0x290 mm/mmu_gather.c:136
 tlb_batch_pages_flush mm/mmu_gather.c:149 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:366 [inline]
 tlb_flush_mmu+0xe9/0x590 mm/mmu_gather.c:373
 zap_pte_range mm/memory.c:1685 [inline]
 zap_pmd_range mm/memory.c:1724 [inline]
 zap_pud_range mm/memory.c:1753 [inline]
 zap_p4d_range mm/memory.c:1774 [inline]
 unmap_page_range+0x1f37/0x3f20 mm/memory.c:1795
 unmap_single_vma+0x194/0x2b0 mm/memory.c:1841
 unmap_vmas+0x22f/0x490 mm/memory.c:1885
 exit_mmap+0x1b8/0xb20 mm/mmap.c:3341
 __mmput+0x12a/0x4d0 kernel/fork.c:1346
 mmput+0x62/0x70 kernel/fork.c:1368
 exit_mm kernel/exit.c:565 [inline]
 do_exit+0x9b7/0x2ba0 kernel/exit.c:861
 do_group_exit+0xd3/0x2a0 kernel/exit.c:1023
 get_signal+0x2616/0x2710 kernel/signal.c:2909
 arch_do_signal_or_restart+0x90/0x7e0 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x14a/0x2a0 kernel/entry/common.c:218

Memory state around the buggy address:
 ffff8880401fff80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888040200000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888040200080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                              ^
 ffff888040200100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888040200180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================