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BUG: KASAN: slab-out-of-bounds in hlist_add_head include/linux/list.h:796 [inline]
BUG: KASAN: slab-out-of-bounds in enqueue_timer kernel/time/timer.c:541 [inline]
BUG: KASAN: slab-out-of-bounds in __internal_add_timer+0x2a6/0x4a0 kernel/time/timer.c:554
Write of size 8 at addr ffff8881ec1271c8 by task syz-executor.3/32239

CPU: 0 PID: 32239 Comm: syz-executor.3 Not tainted 5.4.225-syzkaller-00028-g1641d36fd98f #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/12/2023
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1d8/0x241 lib/dump_stack.c:118
 print_address_description+0x8c/0x630 mm/kasan/report.c:384
 __kasan_report+0xf6/0x130 mm/kasan/report.c:516
 kasan_report+0x30/0x60 mm/kasan/common.c:653
 hlist_add_head include/linux/list.h:796 [inline]
 enqueue_timer kernel/time/timer.c:541 [inline]
 __internal_add_timer+0x2a6/0x4a0 kernel/time/timer.c:554
 internal_add_timer kernel/time/timer.c:604 [inline]
 __mod_timer+0xaad/0x1c90 kernel/time/timer.c:1065
 tun_set_iff+0x8ca/0x1050 drivers/net/tun.c:2874
 __tun_chr_ioctl+0x88e/0x1ee0 drivers/net/tun.c:3169
 do_vfs_ioctl+0x744/0x1730 fs/ioctl.c:47
 ksys_ioctl fs/ioctl.c:742 [inline]
 __do_sys_ioctl fs/ioctl.c:749 [inline]
 __se_sys_ioctl fs/ioctl.c:747 [inline]
 __x64_sys_ioctl+0xd4/0x110 fs/ioctl.c:747
 do_syscall_64+0xcb/0x1c0 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x5c/0xc1

Allocated by task 0:
(stack is not available)

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff8881ec126fb0
 which belongs to the cache shmem_inode_cache of size 744
The buggy address is located 536 bytes inside of
 744-byte region [ffff8881ec126fb0, ffff8881ec127298)
The buggy address belongs to the page:
page:ffffea0007b04900 refcount:1 mapcount:0 mapping:ffff8881f5cfac80 index:0x0 compound_mapcount: 0
flags: 0x8000000000010200(slab|head)
raw: 8000000000010200 dead000000000100 dead000000000122 ffff8881f5cfac80
raw: 0000000000000000 0000000080120012 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL)
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook mm/page_alloc.c:2165 [inline]
 prep_new_page+0x194/0x380 mm/page_alloc.c:2171
 get_page_from_freelist+0x524/0x560 mm/page_alloc.c:3794
 __alloc_pages_nodemask+0x372/0x860 mm/page_alloc.c:4891
 alloc_slab_page+0x39/0x3e0 mm/slub.c:343
 allocate_slab mm/slub.c:1683 [inline]
 new_slab+0x97/0x450 mm/slub.c:1749
 new_slab_objects mm/slub.c:2505 [inline]
 ___slab_alloc+0x320/0x4a0 mm/slub.c:2667
 __slab_alloc+0x5a/0x90 mm/slub.c:2707
 slab_alloc_node mm/slub.c:2792 [inline]
 slab_alloc mm/slub.c:2837 [inline]
 kmem_cache_alloc+0x100/0x210 mm/slub.c:2842
 shmem_alloc_inode+0x16/0x30 mm/shmem.c:3699
 alloc_inode fs/inode.c:231 [inline]
 new_inode_pseudo+0x60/0x210 fs/inode.c:927
 new_inode+0x25/0x1d0 fs/inode.c:956
 shmem_get_inode+0x113/0x630 mm/shmem.c:2252
 shmem_mknod+0x54/0x1a0 mm/shmem.c:2844
 lookup_open fs/namei.c:3309 [inline]
 do_last fs/namei.c:3401 [inline]
 path_openat+0x1ea2/0x3ea0 fs/namei.c:3614
 do_filp_open+0x208/0x450 fs/namei.c:3644
 do_sys_open+0x393/0x7e0 fs/open.c:1113
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1176 [inline]
 __free_pages_ok+0x7fe/0x930 mm/page_alloc.c:1438
 free_the_page mm/page_alloc.c:4953 [inline]
 __free_pages+0x8f/0x250 mm/page_alloc.c:4959
 kfree+0x1ef/0x260 mm/slub.c:4068
 bpf_check+0x4b27/0xb740 kernel/bpf/verifier.c:9704
 bpf_prog_load kernel/bpf/syscall.c:1724 [inline]
 __do_sys_bpf kernel/bpf/syscall.c:2891 [inline]
 __se_sys_bpf+0x77f6/0xbba0 kernel/bpf/syscall.c:2849
 do_syscall_64+0xcb/0x1c0 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x5c/0xc1

Memory state around the buggy address:
 ffff8881ec127080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8881ec127100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8881ec127180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                              ^
 ffff8881ec127200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8881ec127280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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