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Fix crash in filter_servers().

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The bug occurs when we ask lookup_domain() for a server for a domain
which is not a general upstream server, by setting F_DOMAINSRV in the flags.

If there are no possible servers, because there are no upstream servers
defined (for instance, at startup) then the code steps off the end of an
array and SEGVs.

The bug has been latent for some time, but
3e659bd4ec added a new call to lookup_domain()
which can actually trigger the bug if DNSSEC is enabled and a certain
amount of bad luck ensues.

Thanks to the testers extraordinaire at PiHole for reporting this.
This commit is contained in:
Simon Kelley
2025-06-02 22:37:08 +01:00
parent 5846f749e5
commit c378d2c1de
1 changed files with 1 additions and 3 deletions
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4
src/domain-match.c
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@@ -343,10 +343,8 @@ int filter_servers(int seed, int flags, int *lowout, int *highout)
else else
{ {
/* If we want a server for a particular domain, and this one isn't, return nothing. */ /* If we want a server for a particular domain, and this one isn't, return nothing. */
if ((flags & F_DOMAINSRV) && daemon->serverarray[nlow]->domain_len == 0) if (nlow != nhigh && (flags & F_DOMAINSRV) && daemon->serverarray[nlow]->domain_len == 0)
nlow = nhigh; nlow = nhigh;
else
nlow = i;
} }
} }
} }