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https://issues.apache.org/jira/browse/TS-4276?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15195647#comment-15195647
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ASF GitHub Bot commented on TS-4276:
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Github user jacksontj commented on the pull request:
https://github.com/apache/trafficserver/pull/526#issuecomment-196921878
As I'm thinking through this some more, I'm not certain this is a great
solution either. The particular case that I reproduced was that hostdb was full
when returning rr() records. It seems that the `insert` into hostdb can't fail
(as it will eject things if necessary), so really the core issue here is that
we are trying to store some additional information (hostnames, etc.) and we
cannot store them because we are out of space. The current patch I have here is
just returning the HostDBInfo struct, but it didn't put anything in where the
hostnames should be. In the more simple cases (where we are storing the
hostname that we looked up) it is probably preferable to return without a
hostname at all, but in the reverse DNS case that is the primary intent of the
lookup.
Thoughts?
> Segmentation fault when hostdb runs out of space
> ------------------------------------------------
>
> Key: TS-4276
> URL: https://issues.apache.org/jira/browse/TS-4276
> Project: Traffic Server
> Issue Type: Bug
> Reporter: Thomas Jackson
> Assignee: Thomas Jackson
>
> Hostdb assumes that `lookup_done` returns a valid HostDBInfo (as mentioned in
> comments--
> https://github.com/apache/trafficserver/blob/master/iocore/hostdb/HostDB.cc#L1545).
> In actuality lookup_done can actually return NULL in error conditions--
> primarily when it is full
> (https://github.com/apache/trafficserver/blob/master/iocore/hostdb/HostDB.cc#L1363).
> Because of this, if a lookup is being done when hostdb is full, r comes back
> as NULL and we get a segmentation fault that looks like:
> {noformat}
> traffic_server: Segmentation fault (Address not mapped to object [(nil)])
> traffic_server - STACK TRACE:
> ./bin/traffic_server(_Z19crash_logger_invokeiP9siginfo_tPv+0x8e)[0x4ab81e]
> /lib64/libpthread.so.0(+0x109f0)[0x7f991609a9f0]
> ./bin/traffic_server(_ZN18HostDBContinuation8dnsEventEiP7HostEnt+0xebb)[0x6ad5bb]
> ./bin/traffic_server(_ZN8DNSEntry9postEventEiP5Event+0x45)[0x6c5405]
> ./bin/traffic_server(_ZN7EThread13process_eventEP5Eventi+0x8a)[0x7c2c0a]
> ./bin/traffic_server(_ZN7EThread7executeEv+0x7e8)[0x7c3a38]
> ./bin/traffic_server[0x7c26e5]
> /lib64/libpthread.so.0(+0x760a)[0x7f991609160a]
> /lib64/libc.so.6(clone+0x6d)[0x7f9914fa4a4d]
> Segmentation fault (core dumped)
> {noformat}
> Found while trying to repro TS-4207
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