[syzbot] general protection fault in nft_set_elem_expr_alloc

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 6850ec97 Merge branch 'mptcp-fixes-for-5-13'
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=1355504dd00000
kernel config: https://syzkaller.appspot.com/x/.config?x=770708ea7cfd4916
dashboard link: https://syzkaller.appspot.com/bug?extid=ce96ca2b1d0b37c6422d
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1502d517d00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12bbbe13d00000

The issue was bisected to:

commit 05abe4456fa376040f6cc3cc6830d2e328723478
Author: Pablo Neira Ayuso <pa...@netfilter.org>
Date: Wed May 20 13:44:37 2020 +0000

netfilter: nf_tables: allow to register flowtable with no devices

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=10fa1387d00000
final oops: https://syzkaller.appspot.com/x/report.txt?x=12fa1387d00000
console output: https://syzkaller.appspot.com/x/log.txt?x=14fa1387d00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ce96ca...@syzkaller.appspotmail.com
Fixes: 05abe4456fa3 ("netfilter: nf_tables: allow to register flowtable with no devices")

general protection fault, probably for non-canonical address 0xdffffc000000000e: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000070-0x0000000000000077]
CPU: 1 PID: 8438 Comm: syz-executor343 Not tainted 5.13.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:nft_set_elem_expr_alloc+0x17e/0x280 net/netfilter/nf_tables_api.c:5321
Code: 48 c1 ea 03 80 3c 02 00 0f 85 09 01 00 00 49 8b 9d c0 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 8d 7b 70 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 d9 00 00 00 48 8b 5b 70 48 85 db 74 21 e8 9a bd
RSP: 0018:ffffc90000fff338 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 000000000000000e RSI: ffffffff875b1e90 RDI: 0000000000000070
RBP: ffffc90000fff4a0 R08: fffffffffffff000 R09: 0000000000000000
R10: ffffffff875b1e86 R11: 0000000000000000 R12: ffff88802819f200
R13: ffff888028e11000 R14: ffffffff8dca5260 R15: ffffffff8a714120
FS: 0000000002387300(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000190 CR3: 0000000019973000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
nf_tables_newset+0x1b78/0x32a0 net/netfilter/nf_tables_api.c:4370
nfnetlink_rcv_batch+0x1788/0x25c0 net/netfilter/nfnetlink.c:510
nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:631 [inline]
nfnetlink_rcv+0x3af/0x420 net/netfilter/nfnetlink.c:649
netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1340
netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1929
sock_sendmsg_nosec net/socket.c:654 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:674
____sys_sendmsg+0x6e8/0x810 net/socket.c:2350
___sys_sendmsg+0xf3/0x170 net/socket.c:2404
__sys_sendmsg+0xe5/0x1b0 net/socket.c:2433
do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x43f389
Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 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 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffdd09f0258 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000400488 RCX: 000000000043f389
RDX: 0000000000000000 RSI: 00000000200000c0 RDI: 0000000000000004
RBP: 0000000000403370 R08: 0000000000000014 R09: 0000000000400488
R10: 0000000000000074 R11: 0000000000000246 R12: 0000000000403400
R13: 0000000000000000 R14: 00000000004ad018 R15: 0000000000400488
Modules linked in:
---[ end trace dd21b65109300c05 ]---
RIP: 0010:nft_set_elem_expr_alloc+0x17e/0x280 net/netfilter/nf_tables_api.c:5321
Code: 48 c1 ea 03 80 3c 02 00 0f 85 09 01 00 00 49 8b 9d c0 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 8d 7b 70 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 d9 00 00 00 48 8b 5b 70 48 85 db 74 21 e8 9a bd
RSP: 0018:ffffc90000fff338 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 000000000000000e RSI: ffffffff875b1e90 RDI: 0000000000000070
RBP: ffffc90000fff4a0 R08: fffffffffffff000 R09: 0000000000000000
R10: ffffffff875b1e86 R11: 0000000000000000 R12: ffff88802819f200
R13: ffff888028e11000 R14: ffffffff8dca5260 R15: ffffffff8a714120
FS: 0000000002387300(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa0ba0326c0 CR3: 0000000019973000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

[Pablo Neira Ayuso]

It's a real bug. Bisect is not correct though.

I'll post a patch to fix it. Thanks.

[Salvatore Bonaccorso]

Hi Pablo,

So if I see it correctly the fix landed in ad9f151e560b ("netfilter:
nf_tables: initialize set before expression setup") in 5.13-rc7 and
landed as well in 5.12.13. The issue is though still present in the
5.10.y series.

Would it be possible to backport the fix as well to 5.10.y? It is
needed there as well.

Regards,
Salvatore

[Greg KH]

I would need a working backport, as it does not apply cleanly to 5.10.y
:(

thanks,

greg k-h

[Florian Westphal]

Done, sent to stable@.