KASAN: slab-out-of-bounds Write in tun_free_netdev

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 0c0d4177 ANDROID: setlocalversion: fix posix issue with "[["
git tree: android-5.4
console output: https://syzkaller.appspot.com/x/log.txt?x=15fa5e27100000
kernel config: https://syzkaller.appspot.com/x/.config?x=fb5046f17a4c568c
dashboard link: https://syzkaller.appspot.com/bug?extid=0a83abf6a1a3acd6be9b
compiler: Android (6032204 based on r370808) clang version 10.0.1 (https://android.googlesource.com/toolchain/llvm-project 6e765c10313d15c02ab29977a82938f66742c3a9)

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0a83ab...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-out-of-bounds in __hlist_del include/linux/list.h:764 [inline]
BUG: KASAN: slab-out-of-bounds in detach_timer kernel/time/timer.c:815 [inline]
BUG: KASAN: slab-out-of-bounds in detach_if_pending kernel/time/timer.c:832 [inline]
BUG: KASAN: slab-out-of-bounds in try_to_del_timer_sync+0x3ee/0x480 kernel/time/timer.c:1226
Write of size 8 at addr ffff8881d868b188 by task syz-executor.1/14245

CPU: 0 PID: 14245 Comm: syz-executor.1 Not tainted 5.4.52-syzkaller-00272-g0c0d417747d8 #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+0x14a/0x1ce lib/dump_stack.c:118
print_address_description+0x93/0x620 mm/kasan/report.c:374
__kasan_report+0x16d/0x1e0 mm/kasan/report.c:506
kasan_report+0x36/0x60 mm/kasan/common.c:634
__hlist_del include/linux/list.h:764 [inline]
detach_timer kernel/time/timer.c:815 [inline]
detach_if_pending kernel/time/timer.c:832 [inline]
try_to_del_timer_sync+0x3ee/0x480 kernel/time/timer.c:1226
del_timer_sync+0x74/0xe0 kernel/time/timer.c:1365
tun_flow_uninit drivers/net/tun.c:1374 [inline]
tun_free_netdev+0x99/0x3a0 drivers/net/tun.c:2307
netdev_run_todo+0xbe3/0xe90 net/core/dev.c:9351
tun_detach drivers/net/tun.c:743 [inline]
tun_chr_close+0xc0/0xd0 drivers/net/tun.c:3461
__fput+0x27d/0x6c0 fs/file_table.c:280
task_work_run+0x176/0x1a0 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:188 [inline]
exit_to_usermode_loop arch/x86/entry/common.c:163 [inline]
prepare_exit_to_usermode+0x286/0x2e0 arch/x86/entry/common.c:194
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x415d71
Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 04 1b 00 00 c3 48 83 ec 08 e8 0a fc ff ff 48 89 04 24 b8 03 00 00 00 0f 05 <48> 8b 3c 24 48 89 c2 e8 53 fc ff ff 48 89 d0 48 83 c4 08 48 3d 01
RSP: 002b:00007ffdbfa9b130 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000004 RCX: 0000000000415d71
RDX: 0000000000000000 RSI: 0000000000001db6 RDI: 0000000000000003
RBP: 0000000000000001 R08: 000000004d505db6 R09: 000000004d505dba
R10: 00007ffdbfa9b220 R11: 0000000000000293 R12: 0000000000791730
R13: 0000000000093bd7 R14: ffffffffffffffff R15: 000000000078bf0c

The buggy address belongs to the page:
page:ffffea000761a200 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 compound_mapcount: 0
flags: 0x8000000000010000(head)
raw: 8000000000010000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8881d868b080: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
ffff8881d868b100: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
>ffff8881d868b180: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
^
ffff8881d868b200: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
ffff8881d868b280: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.