Re: BUG: unable to handle kernel paging request in fl_dump_key

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit:    1ca0fafd tcp: md5: allow changing MD5 keys in all socket s..
git tree:       net
console output: https://syzkaller.appspot.com/x/log.txt?x=15ec52b7100000
kernel config:  https://syzkaller.appspot.com/x/.config?x=bf3aec367b9ab569
dashboard link: https://syzkaller.appspot.com/bug?extid=9c1be56e9317b795e874
compiler:       gcc (GCC) 10.1.0-syz 20200507
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1062a40b100000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+9c1be56e9317b795e874@xxxxxxxxxxxxxxxxxxxxxxxxx

batman_adv: Cannot find parent device
BUG: unable to handle page fault for address: fffffbfffa2f173f
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 21ffe5067 P4D 21ffe5067 PUD 21ffe4067 PMD 0 
Oops: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 2591 Comm: syz-executor.2 Not tainted 5.8.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:fl_dump_key+0x8d/0x22a0 net/sched/cls_flower.c:2769
Code: 04 f2 04 f2 c7 40 0c 04 f3 f3 f3 65 48 8b 04 25 28 00 00 00 48 89 84 24 00 01 00 00 31 c0 e8 1a 32 0d fb 4c 89 f8 48 c1 e8 03 <42> 0f b6 04 28 84 c0 74 08 3c 03 0f 8e a8 1f 00 00 45 8b 2f 31 ff
RSP: 0018:ffffc900035e72c8 EFLAGS: 00010a06
RAX: 1ffffffffa2f173f RBX: ffffffffd178b819 RCX: ffffffffd178b9f9
RDX: ffff88806c8d2140 RSI: ffffffff86662036 RDI: ffff88809fa14800
RBP: ffff88809fa14800 R08: 0000000000000000 R09: ffff8880953a203c
R10: 0000000000000000 R11: 0000000000000000 R12: ffff888087ce0040
R13: dffffc0000000000 R14: ffff88809fa148b8 R15: ffffffffd178b9f9
FS:  00007f7df9322700(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: fffffbfffa2f173f CR3: 000000006c49a000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 fl_tmplt_dump+0xc9/0x250 net/sched/cls_flower.c:3081
 tc_chain_fill_node+0x48d/0x7c0 net/sched/cls_api.c:2679
 tc_chain_notify+0x187/0x2e0 net/sched/cls_api.c:2705
 tc_ctl_chain+0xb30/0x1000 net/sched/cls_api.c:2891
 rtnetlink_rcv_msg+0x44e/0xad0 net/core/rtnetlink.c:5460
 netlink_rcv_skb+0x15a/0x430 net/netlink/af_netlink.c:2469
 netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
 netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1329
 netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1918
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:672
 ____sys_sendmsg+0x6e8/0x810 net/socket.c:2352
 ___sys_sendmsg+0xf3/0x170 net/socket.c:2406
 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2439
 do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:359
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45cb29
Code: Bad RIP value.
RSP: 002b:00007f7df9321c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000005027a0 RCX: 000000000045cb29
RDX: 0000000000000000 RSI: 00000000200001c0 RDI: 0000000000000009
RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000a44 R14: 00000000004cd2b2 R15: 00007f7df93226d4
Modules linked in:
CR2: fffffbfffa2f173f
---[ end trace aa31af5515bd8e77 ]---
RIP: 0010:fl_dump_key+0x8d/0x22a0 net/sched/cls_flower.c:2769
Code: 04 f2 04 f2 c7 40 0c 04 f3 f3 f3 65 48 8b 04 25 28 00 00 00 48 89 84 24 00 01 00 00 31 c0 e8 1a 32 0d fb 4c 89 f8 48 c1 e8 03 <42> 0f b6 04 28 84 c0 74 08 3c 03 0f 8e a8 1f 00 00 45 8b 2f 31 ff
RSP: 0018:ffffc900035e72c8 EFLAGS: 00010a06
RAX: 1ffffffffa2f173f RBX: ffffffffd178b819 RCX: ffffffffd178b9f9
RDX: ffff88806c8d2140 RSI: ffffffff86662036 RDI: ffff88809fa14800
RBP: ffff88809fa14800 R08: 0000000000000000 R09: ffff8880953a203c
R10: 0000000000000000 R11: 0000000000000000 R12: ffff888087ce0040
R13: dffffc0000000000 R14: ffff88809fa148b8 R15: ffffffffd178b9f9
FS:  00007f7df9322700(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: fffffbfffa2f173f CR3: 000000006c49a000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400