[Dnsmasq-discuss] segv using 2.75 with dnssec

[Andre Heider]

Hi,

I just noticed a crash on my mips based openwrt router.
It looks like it's because of the initial time change on boot, this
device doesn't have a RTC and the time is set using ntp.
I dunno how reproducible this is, maybe it happend before and I just
didn't notice.

Mon Dec  7 17:05:27 2015 daemon.info dnsmasq[1981]: started, version
2.75 cachesize 150
Mon Dec  7 17:05:27 2015 daemon.info dnsmasq[1981]: compile time
options: IPv6 GNU-getopt no-DBus no-i18n no-IDN DHCP DHCPv6 no-Lua
TFTP no-conntrack ipset auth DNSSEC loop-detect inotify
Mon Dec  7 17:05:27 2015 daemon.info dnsmasq[1981]: DNS service
limited to local subnets
Mon Dec  7 17:05:27 2015 daemon.info dnsmasq[1981]: DNSSEC validation enabled
Mon Dec  7 17:05:27 2015 daemon.info dnsmasq-dhcp[1981]: DHCP, IP
range 192.168.0.200 -- 192.168.0.254, lease time 1h
Mon Dec  7 17:05:27 2015 daemon.info dnsmasq[1981]: using nameserver xxx#53
Mon Dec  7 17:05:27 2015 daemon.info dnsmasq[1981]: using nameserver yyy#53
Mon Dec  7 17:05:27 2015 daemon.info dnsmasq[1981]: using local
addresses only for domain internal
Mon Dec  7 17:05:27 2015 daemon.info dnsmasq[1981]: read
/tmp/hosts/dhcp - 1 addresses
Mon Dec  7 17:59:25 2015 daemon.info pppd[1833]: System time change detected.
Mon Dec  7 18:00:10 2015 kern.info kernel: [  122.524730]
Mon Dec  7 18:00:10 2015 kern.info kernel: [  122.524730]
do_page_fault(): sending SIGSEGV to dnsmasq for invalid write access
to 7f282ffc
Mon Dec  7 18:00:10 2015 kern.info kernel: [  122.531825] epc =
00410911 in dnsmasq[400000+2c000]
Mon Dec  7 18:00:10 2015 kern.info kernel: [  122.536700] ra  =
00410959 in dnsmasq[400000+2c000]
Mon Dec  7 18:00:10 2015 kern.info kernel: [  122.541460]

./staging_dir/toolchain-mips_34kc+dsp_gcc-5.2.0_musl-1.1.11/bin/mips-openwrt-linux-gdb
-n ./staging_dir/target-mips_34kc+dsp_musl-1.1.11/root-lantiq/usr/sbin/dnsmasq
(gdb) info symbol 0x00410911
free_frec in section .text
(gdb) info symbol 0x00410959
free_frec + 72 in section .text

./staging_dir/toolchain-mips_34kc+dsp_gcc-5.2.0_musl-1.1.11/bin/mips-openwrt-linux-objdump
-d ./staging_dir/target-mips_34kc+dsp_musl-1.1.11/root-lantiq/usr/sbin/dnsmasq
00410910 <free_frec>:
  410910:   64f5        save    40,ra,s0-s1
  410912:   6704        move    s0,a0
  410914:   9c8c        lw  a0,48(a0)
  410916:   1a00 423d   jal 4108f4 <free_rfd>
  41091a:   6900        li  s1,0
  41091c:   988d        lw  a0,52(s0)
  41091e:   d82c        sw  s1,48(s0)
  410920:   d82b        sw  s1,44(s0)
  410922:   1a00 423d   jal 4108f4 <free_rfd>
  410926:   d833        sw  s1,76(s0)
  410928:   f0a0 988c   lw  a0,172(s0)
  41092c:   d82d        sw  s1,52(s0)
  41092e:   2405        beqz    a0,41093a <free_frec+0x2a>
  410930:   1a00 8f6f   jal 423dbc <blockdata_free>
  410934:   6500        nop
  410936:   f0a0 d82c   sw  s1,172(s0)
  41093a:   f0a0 9890   lw  a0,176(s0)
  41093e:   2406        beqz    a0,41094c <free_frec+0x3c>
  410940:   1a00 8f6f   jal 423dbc <blockdata_free>
  410944:   6500        nop
  410946:   6a00        li  v0,0
  410948:   f0a0 d850   sw  v0,176(s0)
  41094c:   f0c0 9884   lw  a0,196(s0)
  410950:   2403        beqz    a0,410958 <free_frec+0x48>
  410952:   1a00 4244   jal 410910 <free_frec>
  410956:   6500        nop
  410958:   6a00        li  v0,0
  41095a:   f0c0 d844   sw  v0,196(s0)
  41095e:   f0c0 d840   sw  v0,192(s0)
  410962:   6475        restore 40,ra,s0-s1
  410964:   e8a0        jrc ra
  410966:   6500        nop

I don't do asm, but that looks like it might be due to the recursive
'free_frec(f->blocking_query);'?

The config:
dhcp-authoritative
domain-needed
no-hosts
no-resolv
localise-queries
bogus-priv
expand-hosts
local-service
quiet-dhcp
domain=internal
server=/internal/
server=xxx
server=yyy
dhcp-leasefile=/tmp/dhcp.leases
stop-dns-rebind
rebind-localhost-ok
conf-file=/usr/share/dnsmasq/trust-anchors.conf
dnssec
dnssec-timestamp=/etc/dnsmasq.time
dnssec-check-unsigned
dhcp-broadcast=tag:needs-broadcast
addn-hosts=/tmp/hosts
conf-dir=/tmp/dnsmasq.d
dhcp-range=lan,192.168.0.200,192.168.0.254,255.255.255.0,1h
dhcp-option=lan,option:ntp-server,192.168.0.2
dhcp-option=lan,vendor:MSFT,2,1i
no-dhcp-interface=pppoe-wan

Regards,
Andre