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<p>Oh, okay, similar report were reported few hours before this with
subject of "dnsmasq 2.86 crash". Moving discussion into its
thread.<br>
</p>
<div class="moz-cite-prefix">On 10/13/21 16:03, Petr Menšík wrote:<br>
</div>
<blockquote type="cite"
cite="mid:d670f183-868d-09d6-87e7-b549f97b853f@redhat.com">
<p>I have received already multiple reports [1] of crashes in 2.86
version. I thought commit
de372d6914ae20a1f9997815f258efbf3b14c39b might fix that issue,
but even more reports arrived with version including this commit
[2] [3].<br>
</p>
<p>I do not have any coredump available for analysis (yet), but
bugs contain automated backtraces including some variables. It
seems crop_query operation can overflow to some wrong value.
Then qlen gets outside of original domain name char buffer and
process crashes.</p>
<p>I did not find the failing place yet. I suspect order()
function might not always enforce qlen >
daemon->serverarray[try]->domain_len. But without coredump
file I am unsure.</p>
Thread 1 (LWP 3842):
<pre>#0 0x0000558a903382be in lookup_domain (domain=0x558a91fd7cd0 "dns.msftncsi.com", flags=128, lowout=0x7fff41395fe8, highout=0x7fff41395fe4) at /usr/src/debug/dnsmasq-2.86-2.fc35.x86_64/src/domain-match.c:234
rc = <optimized out>
crop_query = <optimized out>
nodots = 0
qlen = 51543
try = <optimized out>
high = <optimized out>
low = <optimized out>
nlow = 0
nhigh = 0
cp = <optimized out>
qdomain = 0x558a91fcb389 <error: Cannot access memory at address 0x558a91fcb389>
#1 0x0000558a90308a2a in forward_query (udpfd=5, udpaddr=0x7fff41396170, dst_addr=0x7fff41396140, dst_iface=5, header=0x558a91fd9e30, plen=34, limit=0x558a91fda030 "", now=1633667814, forward=0x0, ad_reqd=0, do_bit=0) at /usr/src/debug/dnsmasq-2.86-2.fc35.x86_64/src/forward.c:258
flags = 0
fwd_flags = 0
is_dnssec = 0
master = <optimized out>
gotname = 128
hash = 0x558a91fd9b70
oph = 0x0
old_src = 0
first = 12
last = 0
start = 0
subnet = 0
cacheable = 0
forwarded = 0
edns0_len = 94053643165266
pheader = 0x558a91fd9e52 ""
ede = -1
</pre>
<p>Is there any commit after v2.86, which should make this fixed?
Does anyone else met a crash like this and can provide more
debugging? Especially useful would be a way to reproduce. It
seems like nothing very special is required to trigger this bug.</p>
<p>Any thoughts? Fixes maybe?</p>
<p>Cheers,<br>
Petr<br>
</p>
<pre>1. <a class="moz-txt-link-freetext" href="https://bugzilla.redhat.com/show_bug.cgi?id=2009975" moz-do-not-send="true">https://bugzilla.redhat.com/show_bug.cgi?id=2009975</a>
2. <a class="moz-txt-link-freetext" href="https://bugzilla.redhat.com/show_bug.cgi?id=2012151" moz-do-not-send="true">https://bugzilla.redhat.com/show_bug.cgi?id=2012151</a>
3. <a class="moz-txt-link-freetext" href="https://bugzilla.redhat.com/show_bug.cgi?id=2012547" moz-do-not-send="true">https://bugzilla.redhat.com/show_bug.cgi?id=2012547</a>
</pre>
<pre class="moz-signature" cols="72">--
Petr Menšík
Software Engineer
Red Hat, <a class="moz-txt-link-freetext" href="http://www.redhat.com/" moz-do-not-send="true">http://www.redhat.com/</a>
email: <a class="moz-txt-link-abbreviated moz-txt-link-freetext" href="mailto:pemensik@redhat.com" moz-do-not-send="true">pemensik@redhat.com</a>
PGP: DFCF908DB7C87E8E529925BC4931CA5B6C9FC5CB</pre>
</blockquote>
<pre class="moz-signature" cols="72">--
Petr Menšík
Software Engineer
Red Hat, <a class="moz-txt-link-freetext" href="http://www.redhat.com/">http://www.redhat.com/</a>
email: <a class="moz-txt-link-abbreviated" href="mailto:pemensik@redhat.com">pemensik@redhat.com</a>
PGP: DFCF908DB7C87E8E529925BC4931CA5B6C9FC5CB</pre>
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