==================================================================
BUG: KASAN: slab-out-of-bounds in hlist_add_head include/linux/list.h:787 [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 ffff8881e4c6b1c8 by task syz-executor.1/6441

CPU: 0 PID: 6441 Comm: syz-executor.1 Not tainted 5.4.109-syzkaller-00001-g46c5fdececa6 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1d8/0x24e lib/dump_stack.c:118
 print_address_description+0x9b/0x650 mm/kasan/report.c:384
 __kasan_report+0x182/0x260 mm/kasan/report.c:516
 kasan_report+0x30/0x60 mm/kasan/common.c:641
 hlist_add_head include/linux/list.h:787 [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+0xab9/0x1c70 kernel/time/timer.c:1065
 tun_flow_init drivers/net/tun.c:1368 [inline]
 tun_set_iff drivers/net/tun.c:2840 [inline]
 __tun_chr_ioctl+0x3354/0x4b70 drivers/net/tun.c:3096
 do_vfs_ioctl+0x76a/0x1720 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/0x1e0 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x466459
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 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f117dacd188 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 0000000000466459
RDX: 00000000200000c0 RSI: 00000000400454ca RDI: 0000000000000003
RBP: 00000000004bf9fb R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60
R13: 00007ffc68e6934f R14: 00007f117dacd300 R15: 0000000000022000

Allocated by task 6417:
 save_stack mm/kasan/common.c:70 [inline]
 set_track mm/kasan/common.c:78 [inline]
 __kasan_kmalloc+0x137/0x1e0 mm/kasan/common.c:517
 __kmalloc+0x174/0x2f0 mm/slub.c:3903
 kmalloc_array+0x2d/0x40 include/linux/slab.h:619
 kcalloc include/linux/slab.h:629 [inline]
 iter_file_splice_write+0x227/0xf20 fs/splice.c:690
 splice_direct_to_actor+0x4b4/0xb30 fs/splice.c:976
 do_splice_direct+0x28b/0x3e0 fs/splice.c:1064
 do_sendfile+0x8e4/0x1140 fs/read_write.c:1464
 __do_sys_sendfile64 fs/read_write.c:1519 [inline]
 __se_sys_sendfile64 fs/read_write.c:1511 [inline]
 __x64_sys_sendfile64+0x163/0x220 fs/read_write.c:1511
 do_syscall_64+0xcb/0x1e0 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 6417:
 save_stack mm/kasan/common.c:70 [inline]
 set_track mm/kasan/common.c:78 [inline]
 kasan_set_free_info mm/kasan/common.c:333 [inline]
 __kasan_slab_free+0x18a/0x240 mm/kasan/common.c:475
 slab_free_hook mm/slub.c:1454 [inline]
 slab_free_freelist_hook+0x7b/0x150 mm/slub.c:1492
 slab_free mm/slub.c:3072 [inline]
 kfree+0xe0/0x660 mm/slub.c:4061
 iter_file_splice_write+0xcef/0xf20 fs/splice.c:773
 splice_direct_to_actor+0x4b4/0xb30 fs/splice.c:976
 do_splice_direct+0x28b/0x3e0 fs/splice.c:1064
 do_sendfile+0x8e4/0x1140 fs/read_write.c:1464
 __do_sys_sendfile64 fs/read_write.c:1519 [inline]
 __se_sys_sendfile64 fs/read_write.c:1511 [inline]
 __x64_sys_sendfile64+0x163/0x220 fs/read_write.c:1511
 do_syscall_64+0xcb/0x1e0 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff8881e4c6b000
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 200 bytes to the right of
 256-byte region [ffff8881e4c6b000, ffff8881e4c6b100)
The buggy address belongs to the page:
page:ffffea0007931a80 refcount:1 mapcount:0 mapping:ffff8881f5c02780 index:0x0 compound_mapcount: 0
flags: 0x8000000000010200(slab|head)
raw: 8000000000010200 dead000000000100 dead000000000122 ffff8881f5c02780
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8881e4c6b080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881e4c6b100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8881e4c6b180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                              ^
 ffff8881e4c6b200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881e4c6b280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================