Re: kern/52353: [netbsd-8] A crash in icmpv6 code (?)

[Kengo NAKAHARA <k-nakahara%iij.ad.jp@localhost>]

The following reply was made to PR kern/52353; it has been noted by GNATS.

From: Kengo NAKAHARA <k-nakahara%iij.ad.jp@localhost>
To: dmb%yenn.ulegend.net@localhost, gnats-bugs%NetBSD.org@localhost
Cc: kern-bug-people%netbsd.org@localhost, gnats-admin%netbsd.org@localhost, netbsd-bugs%netbsd.org@localhost
Subject: Re: kern/52353: [netbsd-8] A crash in icmpv6 code (?)
Date: Tue, 4 Jul 2017 14:25:25 +0900

 Hi,
 
 Thank you for your quick and detailed reply.
 
 On 2017/07/03 12:30, Dominik Bialy wrote:
 > On Sun, Jul 02, 2017 at 11:35:01PM +0000, Kengo NAKAHARA wrote:
 >> The following reply was made to PR kern/52353; it has been noted by GNATS.
 >>
 >> From: Kengo NAKAHARA <k-nakahara%iij.ad.jp@localhost>
 >> To: gnats-bugs%NetBSD.org@localhost, kern-bug-people%netbsd.org@localhost, gnats-admin%netbsd.org@localhost,
 >>         netbsd-bugs%netbsd.org@localhost
 >> Cc: 
 >> Subject: Re: kern/52353: [netbsd-8] A crash in icmpv6 code (?)
 >> Date: Mon, 3 Jul 2017 08:33:32 +0900
 >>
 >>  Hi,
 >>  
 >>  On 2017/07/01 22:40, dmb%yenn.ulegend.net@localhost wrote:
 >>  > System: NetBSD yenn 8.0_BETA NetBSD 8.0_BETA (YENN) #6: Mon Jun 26 08:49:07 UTC 2017 builds@yenn:/var/obj/sys/arch/amd64/compile/YENN amd64
 >>  
 >>  It seems you use other than GENERIC kernel config.Could you show your
 >>  kernel config?
 >>  
 > It is almost GENERIC with: GATEWAY, and altq* options added.  The setup
 > is somewhat unusual, since I'm using ipf+pf+the old altq
 > 
 > Here's the config:
 > 
 > http://yenn.ulegend.net/~dmb/YENN
 > 
 > Here's dmesg.boot:
 > 
 > http://yenn.ulegend.net/~dmb/dmesg.boot
 > 
 > (The panic in this dmesg is probably unrelated.)
 > 
 > In altq I'm using WFQ over a 0.75 Mbps uplink.
 > 
 >>  > Architecture: x86_64
 >>  > Machine: amd64
 >>  >> Description:
 >>  > yenn# crash -M netbsd.3.core -N netbsd.3
 >>  > Crash version 8.0_BETA, image version 8.0_BETA.
 >>  > System panicked: in6_cksum: mbuf too short for IPv6 header
 >>  > Backtrace from time of crash is available.
 >>  > crash> bt
 >>  > _KERNEL_OPT_NARCNET() at 0
 >>  > ?() at fffffe80a11bcc00
 >>  > vpanic() at vpanic+0x149
 >>  > snprintf() at snprintf
 >>  > in6_cksum() at in6_cksum+0x1a2
 >>  > _icmp6_input() at _icmp6_input+0xb4
 >>  > wqinput_work() at wqinput_work+0x88
 >>  > workqueue_worker() at workqueue_worker+0xbc
 >>  > 
 >>  > yes, IPv6 is via gif(4), but _before_ the patch for MP-fy
 >>  >> How-To-Repeat:
 >>  > 	possibly ping the machine for some time (?) with IPv6 on a gif(4) (?)
 >>  
 >>  Which do you use IPv6 over IPv6 or IPv6 over IPv4?
 >>  
 > IPv6 over IPv4 -- he.net tunnelbroker
 
 Hmm, I guess there may be the issue in combination ALTQ and gif(4).
 So, I try to reproduce it in my simple environment. That is,
     - use two NetBSD-8 machine and connect directly their ethernet ports
     - create IPv6 over IPv4 gif(4) between the two machines
     - apply below WFQ to the gif(4) psrc, pdst ethernet
       ====================
       interface wm2 bandwidth 750000 wfq
       ====================
     - ping6 over gif(4) each other
 However, I cannot reproduce it yet...
 
 By the way, ozaki-r@n.o help me to research this issue. He also implements
 a patch. Could you try below patch?
 ====================
 diff --git a/sys/netinet6/icmp6.c b/sys/netinet6/icmp6.c
 index f740932036d..3b45ba8d785 100644
 --- a/sys/netinet6/icmp6.c
 +++ b/sys/netinet6/icmp6.c
 @@ -494,6 +494,15 @@ _icmp6_input(struct mbuf *m, int off, int proto)
  		goto freeit;
  	}
  
 +	if (m->m_len < sizeof(struct ip6_hdr)) {
 +		m = m_pullup(m, sizeof(struct ip6_hdr));
 +		if (m == NULL) {
 +			ICMP6_STATINC(ICMP6_STAT_TOOSHORT);
 +			icmp6_ifstat_inc(rcvif, ifs6_in_error);
 +			goto freeit;
 +		}
 +	}
 +
  	ip6 = mtod(m, struct ip6_hdr *);
  	IP6_EXTHDR_GET(icmp6, struct icmp6_hdr *, m, off, sizeof(*icmp6));
  	if (icmp6 == NULL) {
 ====================
 
 If the issue is reproduced after applying above patch, could you tell
 me your detailed network configuration and ipf/pf setting? 
 Of course, within the range you can show with no problem.
 
 
 Thanks,
 
 -- 
 //////////////////////////////////////////////////////////////////////
 Internet Initiative Japan Inc.
 
 Device Engineering Section,
 IoT Platform Development Department,
 Network Division,
 Technology Unit
 
 Kengo NAKAHARA <k-nakahara%iij.ad.jp@localhost>