Bus Error when attempting to access MySQL Server using host name

[Andrew Martin]

Binary package hint: libmysqlclient15off

**Only seems to apply to SPARC platform**

When attempting to use any program that acts as a MySQL client (the mysql client itself, PHP's mysql support, etc) from a SPARC machine, the client crashes with a Bus Error if the server's hostname has to be resolved. For example:

(In this case, mysql.internal resolves to 192.168.0.3)

This works fine, as the server name is specified by it's IP address:

<email address hidden>$ mysql -u werdz -h 192.168.0.3 -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 1193400 to server version: 4.0.24_Debian-10sarge2-log

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql> exit
Bye

But when the same server is specified by hostname, it fails:

<email address hidden>$ mysql -u werdz -h mysql.internal -p
Enter password:
Bus error

The exact same behaviour appears when connecting from a PHP script running on the same machine - PHP dies with a Bus Error. It works, however, if the IP address is specified.

The bug is appearing on a Sun Niagara T1 system (in a Sun Fire T2000), however there have been reports of the same bug appearing on other SPARC systems:
http://ubuntuforums.org/showthread.php?t=362855

[Andrew Martin (werdz)]

Command issued:
strace mysql -u werdz -h mysql.internal -p &> mysql-buserror.strace

Password was entered to stdin, and removed from this log file.

No output (except for "Enter Password" prompt) was sent to stdout.

[Andrew Martin (werdz)]

Command issued:
ltrace mysql -u werdz -h mysql.internal -p &> mysql-buserror.ltrace

Password was entered to stdin.

No output (except for "Enter Password" prompt) was sent to stdout.

[Andrew Martin (werdz)]

I've found a workaround (solution?) to this problem.

A stack trace revealed the problem to be occurring in gethostbyname_r in libnss.

Specifying C(XX)FLAGS=DUNDEF_HAVE_GETHOSTBYNAME_R will cause the code to compile without using gethostbyname_r (it will fall back to gethostbyname, using pthread mutexs for thread safety), which solves the problem.

I've created a patch for mysql-5.0.51 that patches configure.in. Running autoconf and then compiling with --without-server will result in a working libmysqlclient (autoconf must be installed).

(This isn't the version that ships with ubuntu, this patch still needs to be worked back into the version that ships with ubuntu).

[Daniel Holbach (dholbach)]

To get your fix included in Ubuntu, try transforming it into a debdiff (http://wiki.ubuntu.com/PackagingGuide/Recipes/Debdiff) and submitting it for review (http://wiki.ubuntu.com/SponsorshipProcess).

[Chuck Short (zulcss)]

Hello,

Thanks for your bug report and making Ubuntu better. I was wondering if you have a reference for this fix in your CFLAGS?

Thanks
chuck

[Mathias Gug (mathiaz)]

It seems that this is a bug in gethostbyname_r in libnss rather than a
problem in mysql. Could it be possible to write a small test case to
make sure that gethostbyname_r doesn't work as expected on sparc64 ?

I'd rather get it fixed in libnss than adding a workaround in mysql.

--
Mathias Gug
Ubuntu Developer http://www.ubuntu.com

[Brian Campbell (bacam)]

We have seen the same problem on Debian/sparc, and suspect that it is the same as http://sources.redhat.com/bugzilla/show_bug.cgi?id=4381 involving glibc making invalid alignment assumptions. We were able to work around the problem by using nscd for host name caching.

[Chuck Short (zulcss)]

This should be fixed in lucid. Please re-open if it isnt.

Regards
chuck