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BUG: KASAN: use-after-free in sysv_new_inode+0xfd3/0x1170 fs/sysv/ialloc.c:153
Read of size 2 at addr ffff888035cb01ce by task syz-executor.4/11263

CPU: 1 PID: 11263 Comm: syz-executor.4 Not tainted 6.10.0-rc4-syzkaller-00301-g5f583a3162ff #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
 print_address_description mm/kasan/report.c:377 [inline]
 print_report+0x169/0x550 mm/kasan/report.c:488
 kasan_report+0x143/0x180 mm/kasan/report.c:601
 sysv_new_inode+0xfd3/0x1170 fs/sysv/ialloc.c:153
 sysv_mknod+0x4e/0xe0 fs/sysv/namei.c:53
 vfs_create+0x23c/0x3d0 fs/namei.c:3207
 do_mknodat+0x447/0x5b0 fs/namei.c:4059
 __do_sys_mknod fs/namei.c:4092 [inline]
 __se_sys_mknod fs/namei.c:4090 [inline]
 __x64_sys_mknod+0x8e/0xa0 fs/namei.c:4090
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff847e7d0a9
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:00007ff848cd80c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000085
RAX: ffffffffffffffda RBX: 00007ff847fb3f80 RCX: 00007ff847e7d0a9
RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000020000040
RBP: 00007ff847eec074 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007ff847fb3f80 R15: 00007ffff680e4a8
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x968 pfn:0x35cb0
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffff7f(buddy)
raw: 00fff00000000000 ffffea00023f5a88 ffffea0002183d08 0000000000000000
raw: 0000000000000968 0000000000000000 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 0x100cca(GFP_HIGHUSER_MOVABLE), pid 20964, tgid 20963 (syz-executor.1), ts 2026800444106, free_ts 2028175892352
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1468
 prep_new_page mm/page_alloc.c:1476 [inline]
 get_page_from_freelist+0x2e43/0x2f00 mm/page_alloc.c:3420
 __alloc_pages_noprof+0x256/0x6c0 mm/page_alloc.c:4678
 alloc_pages_mpol_noprof+0x3e8/0x680 mm/mempolicy.c:2265
 shmem_alloc_folio mm/shmem.c:1628 [inline]
 shmem_alloc_and_add_folio+0x24d/0xdb0 mm/shmem.c:1668
 shmem_get_folio_gfp+0x82d/0x1f50 mm/shmem.c:2055
 shmem_get_folio mm/shmem.c:2160 [inline]
 shmem_write_begin+0x170/0x4d0 mm/shmem.c:2743
 generic_perform_write+0x322/0x640 mm/filemap.c:4015
 shmem_file_write_iter+0xfc/0x120 mm/shmem.c:2919
 new_sync_write fs/read_write.c:497 [inline]
 vfs_write+0xa72/0xc90 fs/read_write.c:590
 ksys_write+0x1a0/0x2c0 fs/read_write.c:643
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 16456 tgid 16456 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1088 [inline]
 free_unref_folios+0xf12/0x19c0 mm/page_alloc.c:2632
 folios_put_refs+0x93a/0xa60 mm/swap.c:1024
 folio_batch_release include/linux/pagevec.h:101 [inline]
 shmem_undo_range+0x6de/0x1df0 mm/shmem.c:1005
 shmem_truncate_range mm/shmem.c:1114 [inline]
 shmem_fallocate+0x497/0x11f0 mm/shmem.c:3117
 lo_fallocate drivers/block/loop.c:335 [inline]
 do_req_filebacked drivers/block/loop.c:509 [inline]
 loop_handle_cmd drivers/block/loop.c:1930 [inline]
 loop_process_work+0x9c1/0x2160 drivers/block/loop.c:1965
 process_one_work kernel/workqueue.c:3231 [inline]
 process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3312
 worker_thread+0x86d/0xd70 kernel/workqueue.c:3393
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Memory state around the buggy address:
 ffff888035cb0080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888035cb0100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888035cb0180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                              ^
 ffff888035cb0200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888035cb0280: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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