BUG: unable to handle kernel NULL pointer dereference in qlink_free (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4d41ead6 Merge tag 'block-5.9-2020-08-28' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1021c761900000
kernel config: https://syzkaller.appspot.com/x/.config?x=891ca5711a9f1650
dashboard link: https://syzkaller.appspot.com/bug?extid=79a9766422a0ca34ca79
compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
CC: [da...@davemloft.net ku...@kernel.org kuz...@ms2.inr.ac.ru linux-...@vger.kernel.org net...@vger.kernel.org yosh...@linux-ipv6.org]

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+79a976...@syzkaller.appspotmail.com

BUG: kernel NULL pointer dereference, address: 0000000000000080
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 91824067 P4D 91824067 PUD 95c1b067 PMD 0
Oops: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 17359 Comm: syz-executor.0 Not tainted 5.9.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:qlink_free+0x16/0xc0 arch/x86/include/asm/paravirt.h:765
Code: b0 0b a5 ff 48 83 c4 08 c3 90 66 2e 0f 1f 84 00 00 00 00 00 41 57 41 56 53 48 83 3d 43 3d 98 07 00 0f 84 a1 00 00 00 49 89 f7 <48> 63 8e 80 00 00 00 9c 58 0f 1f 44 00 00 48 83 3d 34 3d 98 07 00
RSP: 0018:ffffc90017df7778 EFLAGS: 00010286
RAX: ffffea0000000000 RBX: f000ff53f000ff53 RCX: ffffea0000000008
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff888000000000
RBP: ffff888000000000 R08: ffffffff8134ce8c R09: fffffbfff167da9c
R10: fffffbfff167da9c R11: 0000000000000000 R12: ffff888087cf9b40
R13: 00000000000000e0 R14: 0000000000000001 R15: 0000000000000000
FS: 0000000003016940(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000080 CR3: 0000000051b45000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
qlist_free_all mm/kasan/quarantine.c:168 [inline]
quarantine_reduce+0x155/0x1c0 mm/kasan/quarantine.c:261
__kasan_kmalloc+0x32/0x130 mm/kasan/common.c:442
slab_post_alloc_hook+0x3e/0x290 mm/slab.h:518
slab_alloc_node mm/slab.c:3254 [inline]
kmem_cache_alloc_node+0x1e5/0x280 mm/slab.c:3574
__alloc_skb+0x94/0x4f0 net/core/skbuff.c:198
alloc_skb include/linux/skbuff.h:1085 [inline]
nlmsg_new include/net/netlink.h:940 [inline]
inet_netconf_notify_devconf+0x163/0x220 net/ipv4/devinet.c:2093
__devinet_sysctl_unregister net/ipv4/devinet.c:2599 [inline]
devinet_sysctl_unregister net/ipv4/devinet.c:2623 [inline]
inetdev_destroy net/ipv4/devinet.c:324 [inline]
inetdev_event+0x703/0x13b0 net/ipv4/devinet.c:1599
notifier_call_chain kernel/notifier.c:83 [inline]
__raw_notifier_call_chain kernel/notifier.c:361 [inline]
raw_notifier_call_chain+0xe7/0x170 kernel/notifier.c:368
call_netdevice_notifiers_info net/core/dev.c:2033 [inline]
call_netdevice_notifiers_extack net/core/dev.c:2045 [inline]
call_netdevice_notifiers net/core/dev.c:2059 [inline]
rollback_registered_many+0xbc8/0x1380 net/core/dev.c:9283
rollback_registered net/core/dev.c:9328 [inline]
unregister_netdevice_queue+0x2f3/0x4b0 net/core/dev.c:10409
unregister_netdevice include/linux/netdevice.h:2774 [inline]
__tun_detach+0x13b8/0x1c60 drivers/net/tun.c:691
tun_detach drivers/net/tun.c:708 [inline]
tun_chr_close+0xed/0x130 drivers/net/tun.c:3408
__fput+0x34f/0x7b0 fs/file_table.c:281
task_work_run+0x137/0x1c0 kernel/task_work.c:141
tracehook_notify_resume include/linux/tracehook.h:188 [inline]
exit_to_user_mode_loop kernel/entry/common.c:140 [inline]
exit_to_user_mode_prepare+0xfa/0x1b0 kernel/entry/common.c:167
syscall_exit_to_user_mode+0x5e/0x1a0 kernel/entry/common.c:242
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x416f01
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:00007fffa64b5340 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000006 RCX: 0000000000416f01
RDX: 0000000000000000 RSI: 00000000000019bd RDI: 0000000000000005
RBP: 0000000000000001 R08: 00000000f18e59c0 R09: 0000000070fcd209
R10: 00007fffa64b5430 R11: 0000000000000293 R12: 000000000118d940
R13: 000000000118d940 R14: ffffffffffffffff R15: 000000000118d12c
Modules linked in:
CR2: 0000000000000080
---[ end trace 5ddf9bff180393a2 ]---
RIP: 0010:qlink_free+0x16/0xc0 arch/x86/include/asm/paravirt.h:765
Code: b0 0b a5 ff 48 83 c4 08 c3 90 66 2e 0f 1f 84 00 00 00 00 00 41 57 41 56 53 48 83 3d 43 3d 98 07 00 0f 84 a1 00 00 00 49 89 f7 <48> 63 8e 80 00 00 00 9c 58 0f 1f 44 00 00 48 83 3d 34 3d 98 07 00
RSP: 0018:ffffc90017df7778 EFLAGS: 00010286
RAX: ffffea0000000000 RBX: f000ff53f000ff53 RCX: ffffea0000000008
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff888000000000
RBP: ffff888000000000 R08: ffffffff8134ce8c R09: fffffbfff167da9c
R10: fffffbfff167da9c R11: 0000000000000000 R12: ffff888087cf9b40
R13: 00000000000000e0 R14: 0000000000000001 R15: 0000000000000000
FS: 0000000003016940(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000080 CR3: 0000000051b45000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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[syzbot]

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