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<base href="https://bugzilla.netfilter.org/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Iptables fails to match rules with malloc perturberation activated"
href="https://bugzilla.netfilter.org/show_bug.cgi?id=1150">1150</a>
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<th>Summary</th>
<td>Iptables fails to match rules with malloc perturberation activated
</td>
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<th>Product</th>
<td>iptables
</td>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>x86_64
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P5
</td>
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<th>Component</th>
<td>iptables
</td>
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<th>Assignee</th>
<td>netfilter-buglog@lists.netfilter.org
</td>
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<th>Reporter</th>
<td>goeran@uddeborg.se
</td>
</tr></table>
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<div>
<pre>On my Fedora system, I've upgraded to Fedora 26 versions of iptables and, in
case it matters, glibc.
iptables-1.6.1-2.fc26.x86_64
glibc-2.25-4.fc26.x86_64
I also have the debugmode package installed, which sets the environment
variable MALLOC_PERTURB_ to a random value. The variable is meant to
"detecting errors where programs incorrectly rely on allocated memory being
initialized to zero, or reuse values in memory that has already been freed."
It appears iptables in some cases do this.
I haven't figured out exactly what conditions trigger the bug, but here is one
way to reliably reproduce the behaviour:
iptables -t nat -N testchain
iptables -t nat -A testchain -j SNAT --to-source 1.2.3.4
MALLOC_PERTURB_=42 iptables -t nat -D testchain -j SNAT --to-source 1.2.3.4
The last command gives the error message
iptables: No chain/target/match by that name.
The rule I try to remove is still present. If I disable malloc perturberation
by setting the variable to 0, the command succeeds
MALLOC_PERTURB_=0 iptables -t nat -D testchain -j SNAT --to-source 1.2.3.4
This gives no error message, and the rule is indeed gone.</pre>
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