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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 ffff8880121761ce by task syz.5.2096/13574

CPU: 1 UID: 0 PID: 13574 Comm: syz.5.2096 Not tainted 6.11.0-rc1-syzkaller-00272-g17712b7ea075 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:93 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:119
 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
 lookup_open fs/namei.c:3578 [inline]
 open_last_lookups fs/namei.c:3647 [inline]
 path_openat+0x1a9c/0x3470 fs/namei.c:3883
 do_filp_open+0x235/0x490 fs/namei.c:3913
 do_sys_openat2+0x13e/0x1d0 fs/open.c:1416
 do_sys_open fs/open.c:1431 [inline]
 __do_sys_openat fs/open.c:1447 [inline]
 __se_sys_openat fs/open.c:1442 [inline]
 __x64_sys_openat+0x247/0x2a0 fs/open.c:1442
 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: 0033:0x7facef9779f9
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:00007facf06fd048 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007facefb05f80 RCX: 00007facef9779f9
RDX: 000000000000275a RSI: 0000000020000080 RDI: ffffffffffffff9c
RBP: 00007facef9e58ee R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007facefb05f80 R15: 00007ffdff6cb718
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x282 pfn:0x12176
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea0000485d48 ffffea0000485dc8 0000000000000000
raw: 0000000000000282 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 0x140cca(GFP_HIGHUSER_MOVABLE|__GFP_COMP), pid 18919, tgid 18918 (syz.4.3397), ts 1322423396654, free_ts 1323802306121
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1493
 prep_new_page mm/page_alloc.c:1501 [inline]
 get_page_from_freelist+0x2e4c/0x2f10 mm/page_alloc.c:3442
 __alloc_pages_noprof+0x256/0x6c0 mm/page_alloc.c:4700
 alloc_pages_mpol_noprof+0x3e8/0x680 mm/mempolicy.c:2263
 folio_alloc_mpol_noprof+0x36/0x50 mm/mempolicy.c:2281
 shmem_alloc_folio mm/shmem.c:1726 [inline]
 shmem_alloc_and_add_folio+0x2ce/0x14e0 mm/shmem.c:1786
 shmem_get_folio_gfp+0x8dc/0x2370 mm/shmem.c:2192
 shmem_fault+0x252/0x6f0 mm/shmem.c:2392
 __do_fault+0x137/0x460 mm/memory.c:4655
 do_read_fault mm/memory.c:5061 [inline]
 do_fault mm/memory.c:5191 [inline]
 do_pte_missing mm/memory.c:3947 [inline]
 handle_pte_fault+0x3b24/0x6eb0 mm/memory.c:5522
 __handle_mm_fault mm/memory.c:5665 [inline]
 handle_mm_fault+0x1029/0x1980 mm/memory.c:5833
 faultin_page mm/gup.c:1194 [inline]
 __get_user_pages+0x6ec/0x16a0 mm/gup.c:1493
 populate_vma_page_range+0x264/0x330 mm/gup.c:1932
 __mm_populate+0x27a/0x460 mm/gup.c:2035
 mm_populate include/linux/mm.h:3415 [inline]
 vm_mmap_pgoff+0x2c3/0x3d0 mm/util.c:593
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
page last free pid 18921 tgid 18918 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1094 [inline]
 free_unref_folios+0x103a/0x1b00 mm/page_alloc.c:2660
 folios_put_refs+0x76e/0x860 mm/swap.c:1039
 folio_batch_release include/linux/pagevec.h:101 [inline]
 shmem_undo_range+0x6de/0x1df0 mm/shmem.c:1023
 shmem_truncate_range mm/shmem.c:1132 [inline]
 shmem_evict_inode+0x29b/0xa80 mm/shmem.c:1260
 evict+0x2aa/0x630 fs/inode.c:669
 __dentry_kill+0x20d/0x630 fs/dcache.c:610
 dput+0x19f/0x2b0 fs/dcache.c:852
 __fput+0x5f8/0x8a0 fs/file_table.c:430
 task_work_run+0x251/0x310 kernel/task_work.c:228
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0xa2f/0x27f0 kernel/exit.c:882
 do_group_exit+0x207/0x2c0 kernel/exit.c:1031
 get_signal+0x16a1/0x1740 kernel/signal.c:2917
 arch_do_signal_or_restart+0x96/0x860 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+0xc9/0x370 kernel/entry/common.c:218
 do_syscall_64+0x100/0x230 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff888012176080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888012176100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888012176180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                              ^
 ffff888012176200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888012176280: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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