sysv_free_block: flc_count > flc_size
sysv_free_block: flc_count > flc_size
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+0x78c/0x960 fs/sysv/balloc.c:113
Read of size 4 at addr ffff888071f4c0c8 by task syz-executor.0/5492

CPU: 0 PID: 5492 Comm: syz-executor.0 Not tainted 6.7.0-rc7-syzkaller-00041-gf016f7547aee #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e7/0x2d0 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0x163/0x540 mm/kasan/report.c:475
 kasan_report+0x142/0x170 mm/kasan/report.c:588
 sysv_new_block+0x78c/0x960 fs/sysv/balloc.c:113
 alloc_branch fs/sysv/itree.c:134 [inline]
 get_block+0x309/0x1710 fs/sysv/itree.c:255
 __block_write_begin_int+0x54d/0x1ad0 fs/buffer.c:2119
 __block_write_begin fs/buffer.c:2168 [inline]
 block_write_begin+0x9b/0x1e0 fs/buffer.c:2227
 sysv_write_begin+0x31/0x70 fs/sysv/itree.c:490
 generic_perform_write+0x31b/0x630 mm/filemap.c:3927
 generic_file_write_iter+0xaf/0x310 mm/filemap.c:4048
 call_write_iter include/linux/fs.h:2020 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x792/0xb20 fs/read_write.c:584
 ksys_write+0x1a0/0x2c0 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x45/0x110 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b
RIP: 0033:0x7fee2307c8d9
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:00007fee23db10c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fee2319bf80 RCX: 00007fee2307c8d9
RDX: 00000000fffffd5e RSI: 000000002000ad00 RDI: 0000000000000004
RBP: 00007fee230d8b20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007fee2319bf80 R15: 00007fff1a1a5ca8
 </TASK>

The buggy address belongs to the physical page:
page:ffffea0001c7d300 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x71f4c
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000000000001 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 5050, tgid 5048 (syz-fuzzer), ts 62502594779, free_ts 65248714986
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1e6/0x210 mm/page_alloc.c:1537
 prep_new_page mm/page_alloc.c:1544 [inline]
 get_page_from_freelist+0x33ea/0x3570 mm/page_alloc.c:3312
 __alloc_pages+0x255/0x680 mm/page_alloc.c:4568
 alloc_pages_mpol+0x3de/0x640 mm/mempolicy.c:2133
 vma_alloc_folio+0xf3/0x3f0 mm/mempolicy.c:2172
 do_anonymous_page mm/memory.c:4172 [inline]
 do_pte_missing mm/memory.c:3729 [inline]
 handle_pte_fault mm/memory.c:5039 [inline]
 __handle_mm_fault mm/memory.c:5180 [inline]
 handle_mm_fault+0x238a/0x6680 mm/memory.c:5345
 do_user_addr_fault arch/x86/mm/fault.c:1364 [inline]
 handle_page_fault arch/x86/mm/fault.c:1505 [inline]
 exc_page_fault+0x456/0x870 arch/x86/mm/fault.c:1561
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:570
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1137 [inline]
 free_unref_page_prepare+0x931/0xa60 mm/page_alloc.c:2347
 free_unref_page_list+0x5a0/0x840 mm/page_alloc.c:2533
 release_pages+0x2117/0x2400 mm/swap.c:1042
 tlb_batch_pages_flush mm/mmu_gather.c:98 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:293 [inline]
 tlb_flush_mmu+0x34c/0x4e0 mm/mmu_gather.c:300
 tlb_finish_mmu+0xd4/0x1f0 mm/mmu_gather.c:392
 exit_mmap+0x4d3/0xc60 mm/mmap.c:3321
 __mmput+0x115/0x3c0 kernel/fork.c:1349
 exit_mm+0x21f/0x300 kernel/exit.c:567
 do_exit+0x9af/0x2740 kernel/exit.c:856
 do_group_exit+0x206/0x2c0 kernel/exit.c:1018
 get_signal+0x1769/0x1840 kernel/signal.c:2904
 arch_do_signal_or_restart+0x96/0x860 arch/x86/kernel/signal.c:309
 exit_to_user_mode_loop+0x6a/0x100 kernel/entry/common.c:168
 exit_to_user_mode_prepare+0xb1/0x150 kernel/entry/common.c:204
 __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline]
 syscall_exit_to_user_mode+0x69/0x2a0 kernel/entry/common.c:296
 do_syscall_64+0x52/0x110 arch/x86/entry/common.c:89

Memory state around the buggy address:
 ffff888071f4bf80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888071f4c000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888071f4c080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                              ^
 ffff888071f4c100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888071f4c180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================