syz.1.20: attempt to access beyond end of device
loop1: rw=0, sector=6491536, nr_sectors = 2 limit=128
Buffer I/O error on dev loop1, logical block 3245768, async page read
==================================================================
BUG: KASAN: use-after-free in sysv_new_inode+0x10c5/0x1270 fs/sysv/ialloc.c:153
Read of size 2 at addr ffff88806d3101ce by task syz.1.20/5946

CPU: 1 PID: 5946 Comm: syz.1.20 Not tainted 6.6.101-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xac/0x220 mm/kasan/report.c:468
 kasan_report+0x117/0x150 mm/kasan/report.c:581
 sysv_new_inode+0x10c5/0x1270 fs/sysv/ialloc.c:153
 sysv_mknod+0x4e/0xe0 fs/sysv/namei.c:53
 lookup_open fs/namei.c:3488 [inline]
 open_last_lookups fs/namei.c:3556 [inline]
 path_openat+0x1277/0x3190 fs/namei.c:3786
 do_filp_open+0x1c5/0x3d0 fs/namei.c:3816
 do_sys_openat2+0x12c/0x1c0 fs/open.c:1419
 do_sys_open fs/open.c:1434 [inline]
 __do_sys_openat fs/open.c:1450 [inline]
 __se_sys_openat fs/open.c:1445 [inline]
 __x64_sys_openat+0x139/0x160 fs/open.c:1445
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7feb01b8ebe9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007feb029b9038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007feb01db5fa0 RCX: 00007feb01b8ebe9
RDX: 000000000000275a RSI: 0000200000000080 RDI: ffffffffffffff9c
RBP: 00007feb01c11e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007feb01db6038 R14: 00007feb01db5fa0 R15: 00007ffdb4b5ec28
 </TASK>

The buggy address belongs to the physical page:
page:ffffea0001b4c400 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x6d310
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffff7f(buddy)
raw: 00fff00000000000 ffffea0001b48408 ffffea0001b4d008 0000000000000000
raw: 0000000000000001 0000000000000004 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 0x140cca(GFP_HIGHUSER_MOVABLE|__GFP_COMP), pid 5925, tgid 5923 (syz.2.12), ts 104376380696, free_ts 107143719231
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1cd/0x210 mm/page_alloc.c:1554
 prep_new_page mm/page_alloc.c:1561 [inline]
 get_page_from_freelist+0x195c/0x19f0 mm/page_alloc.c:3191
 __alloc_pages+0x1e3/0x460 mm/page_alloc.c:4457
 __folio_alloc+0x10/0x20 mm/page_alloc.c:4489
 vma_alloc_folio+0x47a/0x8f0 mm/mempolicy.c:2242
 shmem_alloc_folio+0x179/0x230 mm/shmem.c:1680
 shmem_alloc_and_acct_folio+0x189/0x630 mm/shmem.c:1705
 shmem_get_folio_gfp+0xcde/0x2ac0 mm/shmem.c:2042
 shmem_get_folio mm/shmem.c:2165 [inline]
 shmem_write_begin+0xf2/0x420 mm/shmem.c:2707
 generic_perform_write+0x2fb/0x5b0 mm/filemap.c:4016
 shmem_file_write_iter+0xfb/0x120 mm/shmem.c:2884
 call_write_iter include/linux/fs.h:2018 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x43b/0x940 fs/read_write.c:584
 ksys_write+0x147/0x250 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1154 [inline]
 free_unref_page_prepare+0x7ce/0x8e0 mm/page_alloc.c:2336
 free_unref_page_list+0xbe/0x860 mm/page_alloc.c:2475
 release_pages+0x1fa0/0x2220 mm/swap.c:1022
 __folio_batch_release+0x71/0xe0 mm/swap.c:1042
 folio_batch_release include/linux/pagevec.h:83 [inline]
 shmem_undo_range+0x5d0/0x1a40 mm/shmem.c:1027
 shmem_truncate_range mm/shmem.c:1136 [inline]
 shmem_evict_inode+0x273/0xa70 mm/shmem.c:1265
 evict+0x486/0x870 fs/inode.c:705
 __dentry_kill+0x431/0x650 fs/dcache.c:611
 dentry_kill+0xb8/0x290 fs/dcache.c:-1
 dput+0xfe/0x1e0 fs/dcache.c:918
 __fput+0x5e5/0x970 fs/file_table.c:392
 task_work_run+0x1ce/0x250 kernel/task_work.c:239
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
 exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:87

Memory state around the buggy address:
 ffff88806d310080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88806d310100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88806d310180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                              ^
 ffff88806d310200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88806d310280: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================