BUG: unable to handle kernel paging request in tcf_action_destroy

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    425c075d Merge branch 'tun-debug'
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=12a97f0de00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=598678fc6e800071
dashboard link: https://syzkaller.appspot.com/bug?extid=e30bd6a0f27d4d638567
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

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

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+e30bd6a0f27d4d638567@xxxxxxxxxxxxxxxxxxxxxxxxx

BUG: unable to handle page fault for address: ffffffffffffffff
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 9670067 P4D 9670067 PUD 9672067 PMD 0 
Oops: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 26046 Comm: syz-executor.3 Not tainted 5.6.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:tcf_action_destroy+0x75/0x150 net/sched/act_api.c:720
Code: 83 c3 08 89 ee e8 3b 27 48 fb 83 fd 20 0f 84 ae 00 00 00 e8 bd 25 48 fb 48 89 d8 48 c1 e8 03 42 80 3c 28 00 0f 85 ae 00 00 00 <4c> 8b 3b 4d 85 ff 0f 84 8b 00 00 00 e8 9a 25 48 fb 4c 89 f8 48 c7
RSP: 0018:ffffc90001c57028 EFLAGS: 00010246
RAX: 1fffffffffffffff RBX: ffffffffffffffff RCX: ffffc9000fec9000
RDX: 00000000000008d1 RSI: ffffffff8629ecd3 RDI: ffffffffffffffff
RBP: 0000000000000000 R08: ffff88805b4861c0 R09: ffffed1015ce7074
R10: ffffed1015ce7073 R11: ffff8880ae73839b R12: 0000000000000000
R13: dffffc0000000000 R14: 0000000000000001 R15: 0000000000000000
FS:  00007f4bd1960700(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffff CR3: 000000004a795000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 tcf_exts_destroy+0x42/0xc0 net/sched/cls_api.c:3001
 tcf_exts_change+0xf4/0x150 net/sched/cls_api.c:3059
 tcindex_set_parms+0xed8/0x1a00 net/sched/cls_tcindex.c:456
 tcindex_change+0x203/0x2e0 net/sched/cls_tcindex.c:518
 tc_new_tfilter+0xa59/0x20b0 net/sched/cls_api.c:2103
 rtnetlink_rcv_msg+0x810/0xad0 net/core/rtnetlink.c:5431
 netlink_rcv_skb+0x15a/0x410 net/netlink/af_netlink.c:2478
 netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
 netlink_unicast+0x537/0x740 net/netlink/af_netlink.c:1329
 netlink_sendmsg+0x882/0xe10 net/netlink/af_netlink.c:1918
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:672
 ____sys_sendmsg+0x6b9/0x7d0 net/socket.c:2343
 ___sys_sendmsg+0x100/0x170 net/socket.c:2397
 __sys_sendmsg+0xec/0x1b0 net/socket.c:2430
 do_syscall_64+0xf6/0x790 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c4a9
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f4bd195fc78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f4bd19606d4 RCX: 000000000045c4a9
RDX: 0000000000000000 RSI: 00000000200001c0 RDI: 0000000000000003
RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000009fa R14: 00000000004cc777 R15: 000000000076bf2c
Modules linked in:
CR2: ffffffffffffffff
---[ end trace c654cd1e2ba461f1 ]---
RIP: 0010:tcf_action_destroy+0x75/0x150 net/sched/act_api.c:720
Code: 83 c3 08 89 ee e8 3b 27 48 fb 83 fd 20 0f 84 ae 00 00 00 e8 bd 25 48 fb 48 89 d8 48 c1 e8 03 42 80 3c 28 00 0f 85 ae 00 00 00 <4c> 8b 3b 4d 85 ff 0f 84 8b 00 00 00 e8 9a 25 48 fb 4c 89 f8 48 c7
RSP: 0018:ffffc90001c57028 EFLAGS: 00010246
RAX: 1fffffffffffffff RBX: ffffffffffffffff RCX: ffffc9000fec9000
RDX: 00000000000008d1 RSI: ffffffff8629ecd3 RDI: ffffffffffffffff
RBP: 0000000000000000 R08: ffff88805b4861c0 R09: ffffed1015ce7074
R10: ffffed1015ce7073 R11: ffff8880ae73839b R12: 0000000000000000
R13: dffffc0000000000 R14: 0000000000000001 R15: 0000000000000000
FS:  00007f4bd1960700(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffff CR3: 000000004a795000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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