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 ffff888038f6c0c8 by task syz-executor.0/5473

CPU: 0 PID: 5473 Comm: syz-executor.0 Not tainted 6.9.0-rc1-syzkaller-g4cece7649650 #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+0x261/0x15a0 fs/sysv/itree.c:254
 __block_write_begin_int+0x4fb/0x16e0 fs/buffer.c:2105
 __block_write_begin fs/buffer.c:2154 [inline]
 block_write_begin+0xb1/0x4a0 fs/buffer.c:2213
 sysv_write_begin+0x31/0xe0 fs/sysv/itree.c:490
 generic_perform_write+0x272/0x620 mm/filemap.c:3974
 __generic_file_write_iter+0x1fd/0x240 mm/filemap.c:4069
 generic_file_write_iter+0xe7/0x350 mm/filemap.c:4095
 call_write_iter include/linux/fs.h:2108 [inline]
 new_sync_write fs/read_write.c:497 [inline]
 vfs_write+0x6db/0x1100 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+0xd2/0x260 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x6d/0x75
RIP: 0033:0x7f289547dda9
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:00007f28962c30c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f28955abf80 RCX: 00007f289547dda9
RDX: 00000000fffffd5e RSI: 000000002000ad00 RDI: 0000000000000004
RBP: 00007f28954ca47a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f28955abf80 R15: 00007ffe359463f8
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x38f6c
flags: 0xfff80000000000(node=0|zone=1|lastcpupid=0xfff)
page_type: 0xffffffff()
raw: 00fff80000000000 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 0x152c4a(GFP_NOFS|__GFP_HIGHMEM|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_HARDWALL|__GFP_MOVABLE), pid 5198, tgid 5198 (syz-executor), ts 60568508178, free_ts 86362373354
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x2d4/0x350 mm/page_alloc.c:1534
 prep_new_page mm/page_alloc.c:1541 [inline]
 get_page_from_freelist+0xa28/0x3780 mm/page_alloc.c:3317
 __alloc_pages+0x22b/0x2460 mm/page_alloc.c:4575
 alloc_pages_mpol+0x275/0x610 mm/mempolicy.c:2264
 folio_alloc+0x1e/0x40 mm/mempolicy.c:2342
 filemap_alloc_folio+0x3ba/0x490 mm/filemap.c:984
 page_cache_ra_unbounded+0x1a5/0x5a0 mm/readahead.c:247
 do_page_cache_ra mm/readahead.c:299 [inline]
 page_cache_ra_order+0x64b/0x9a0 mm/readahead.c:539
 ondemand_readahead+0x520/0x1140 mm/readahead.c:661
 page_cache_async_ra mm/readahead.c:710 [inline]
 page_cache_async_ra+0x123/0x150 mm/readahead.c:692
 filemap_readahead mm/filemap.c:2480 [inline]
 filemap_get_pages+0x359/0x1840 mm/filemap.c:2521
 filemap_read+0x3a8/0xd10 mm/filemap.c:2601
 generic_file_read_iter+0x350/0x460 mm/filemap.c:2782
 ext4_file_read_iter+0x1dc/0x6c0 fs/ext4/file.c:147
 __kernel_read+0x3ec/0xb20 fs/read_write.c:434
 integrity_kernel_read+0x7f/0xb0 security/integrity/iint.c:28
page last free pid 5413 tgid 5413 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1141 [inline]
 free_unref_page_prepare+0x527/0xb10 mm/page_alloc.c:2347
 free_unref_folios+0x256/0xad0 mm/page_alloc.c:2536
 folios_put_refs+0x49c/0x750 mm/swap.c:1034
 folio_batch_release include/linux/pagevec.h:101 [inline]
 truncate_inode_pages_range+0x326/0xe80 mm/truncate.c:362
 ext4_evict_inode+0x2cc/0x17a0 fs/ext4/inode.c:193
 evict+0x2ed/0x6c0 fs/inode.c:667
 iput_final fs/inode.c:1741 [inline]
 iput.part.0+0x5a8/0x7f0 fs/inode.c:1767
 iput+0x5c/0x80 fs/inode.c:1757
 do_unlinkat+0x613/0x750 fs/namei.c:4409
 __do_sys_unlink fs/namei.c:4450 [inline]
 __se_sys_unlink fs/namei.c:4448 [inline]
 __x64_sys_unlink+0xc7/0x110 fs/namei.c:4448
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xd2/0x260 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x6d/0x75

Memory state around the buggy address:
 ffff888038f6bf80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888038f6c000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888038f6c080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                              ^
 ffff888038f6c100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888038f6c180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================