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Date:	Sun, 04 May 2014 10:25:58 +0300
From:	Denys Fedoryshchenko <nuclearcat@...learcat.com>
To:	netdev@...r.kernel.org, kaber@...sh.net, kadlec@...ckhole.kfki.hu,
	Pablo <pablo@...filter.org>
Subject: Re: nft 2.0, NULL pointer dereference in 3.14.1

Hi

I bit more debugging and found that problem is happening at:

> sock = netlink_lookup(sock_net(ssk), ssk->sk_protocol, portid);

ssk is NULL

After checking, i noticed in nfnetlink.c
nfnetlink_rcv_batch() function

We have
nskb->sk = oskb->sk;
skb = nskb;

I am matching condition
ss = rcu_dereference_protected(table[subsys_id].subsys,
        lockdep_is_held(&table[subsys_id].mutex));
if (!ss) {

And then
nfnl_unlock(subsys_id);
kfree_skb(nskb);
return netlink_ack(skb, nlh, -EOPNOTSUPP);

If i am not wrong, nskb same pointer as skb, so we are giving 
netlink_ack freed pointer?
Is it "use after free()" ?

If yes, then it seems attached patch fixing my issue. Please let me 
know, if it is ok and i should submit it.


On 2014-04-19 10:36, Denys Fedoryshchenko wrote:
> Hi
> 
> While trying nft got kernel NULL dereference
> extreme ~ # nft -v
> nftables v0.2 (Support Edward Snowden)
> extreme ~ # uname -a
> Linux extreme 3.14.1-extreme-stable #1 SMP Sat Apr 19 10:23:48 EEST
> 2014 x86_64 Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz GenuineIntel
> GNU/Linux
> 
> Command i tried (nothing else entered before it):
> nft add rule filter icmp-chain counter
> 
> kernel message:
> [   44.071555] Netfilter messages via NETLINK v0.30.
> [   44.072253] BUG: unable to handle kernel NULL pointer dereference
> at 0000000000000119
> [   44.072264] IP: [<ffffffff8171db1f>] 
> netlink_getsockbyportid+0xf/0x70
> [   44.072272] PGD 7f2b74067 PUD 7f2b73067 PMD 0
> [   44.072277] Oops: 0000 [#1] SMP
> [   44.072280] Modules linked in: nfnetlink ftdi_sio usbserial
> usb_storage x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel
> kvm iTCO_wdt iTCO_vendor_support mei_me mei lpc_ich mfd_core
> [   44.072301] CPU: 4 PID: 2573 Comm: nft Not tainted 
> 3.14.1-extreme-stable #1
> [   44.072304] Hardware name:                  /DH87MC, BIOS
> MCH8710H.86A.0154.2014.0123.1542 01/23/2014
> [   44.072308] task: ffff8807f5195340 ti: ffff8807d4c36000 task.ti:
> ffff8807d4c36000
> [   44.072311] RIP: 0010:[<ffffffff8171db1f>]  [<ffffffff8171db1f>]
> netlink_getsockbyportid+0xf/0x70
> [   44.072317] RSP: 0018:ffff8807d4c37a90  EFLAGS: 00010202
> [   44.072319] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 
> 0000000000000028
> [   44.072322] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 
> 0000000000000000
> [   44.072325] RBP: ffff8807d4c37a98 R08: 0000000000000000 R09: 
> ffff8807f85b0028
> [   44.072328] R10: 00000000ffffffff R11: 0000000000000000 R12: 
> ffff8807f5de2900
> [   44.072331] R13: 0000000000000000 R14: 0000000000000000 R15: 
> 0000000000000018
> [   44.072335] FS:  00007fa028b25700(0000) GS:ffff88081ed00000(0000)
> knlGS:0000000000000000
> [   44.072338] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [   44.072341] CR2: 0000000000000119 CR3: 00000007f370d000 CR4: 
> 00000000001407e0
> [   44.072343] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 
> 0000000000000000
> [   44.072346] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 
> 0000000000000400
> [   44.072349] Stack:
> [   44.072351]  0000000000000040 ffff8807d4c37ad0 ffffffff8171fd81
> 0000000000000000
> [   44.072357]  ffff8807f5de2900 ffff8807f5de2900 00000000ffffffa1
> ffff8807f85b1600
> [   44.072363]  ffff8807d4c37b08 ffffffff817206c9 ffff8807f85b1600
> ffff8807f5de3400
> [   44.072369] Call Trace:
> [   44.072373]  [<ffffffff8171fd81>] netlink_unicast+0x91/0x200
> [   44.072377]  [<ffffffff817206c9>] netlink_ack+0x99/0x110
> [   44.072381]  [<ffffffffa004b951>] nfnetlink_rcv+0x3c1/0x408 
> [nfnetlink]
> [   44.072385]  [<ffffffff8171fde3>] netlink_unicast+0xf3/0x200
> [   44.072389]  [<ffffffff817201ef>] netlink_sendmsg+0x2ff/0x740
> [   44.072394]  [<ffffffff81044752>] ? __mmdrop+0x62/0x90
> [   44.072398]  [<ffffffff816dafdb>] sock_sendmsg+0x8b/0xc0
> [   44.072403]  [<ffffffff812f1af5>] ? 
> copy_user_enhanced_fast_string+0x5/0x10
> [   44.072406]  [<ffffffff816dbb6c>] ? move_addr_to_kernel+0x2c/0x50
> [   44.072410]  [<ffffffff816db423>] ___sys_sendmsg+0x3c3/0x3d0
> [   44.072415]  [<ffffffff811301ba>] ? handle_mm_fault+0xa9a/0xc60
> [   44.072420]  [<ffffffff811362d6>] ? mmap_region+0x166/0x5a0
> [   44.072424]  [<ffffffff817da84c>] ? __do_page_fault+0x1dc/0x510
> [   44.072428]  [<ffffffff812b8b2c>] ? apparmor_capable+0x1c/0x60
> [   44.072435]  [<ffffffff817d6e9a>] ? _raw_spin_unlock_bh+0x1a/0x20
> [   44.072439]  [<ffffffff816dfc86>] ? release_sock+0x106/0x150
> [   44.072443]  [<ffffffff816dc212>] __sys_sendmsg+0x42/0x80
> [   44.072446]  [<ffffffff816dc262>] SyS_sendmsg+0x12/0x20
> [   44.072450]  [<ffffffff817df616>] system_call_fastpath+0x1a/0x1f
> [   44.072453] Code: 41 5d 41 5e 5d c3 66 0f 1f 44 00 00 f0 ff 43 4c
> eb e1 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 89 f2 48 89 e5
> 53 48 89 fb <0f> b6 b7 19 01 00 00 48 8b 7f 30 e8 f1 fe ff ff 48 89 c7
> 48 c7
> [   44.072963] RIP  [<ffffffff8171db1f>] 
> netlink_getsockbyportid+0xf/0x70
> [   44.073253]  RSP <ffff8807d4c37a90>
> [   44.073524] CR2: 0000000000000119
> [   44.074757] ---[ end trace f3a9846ab3cb7550 ]---
> 
> Please let me know if more information required.
> Thanks!

View attachment "use_after_free.patch" of type "text/x-diff" (628 bytes)

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