Perl script suffers random __fortify_fail errors, but continues to run without any errors. Should I be worried?

Question

I'm currently running a pretty intensive Perl script on an Amazon EC2 server. The script should take a couple of weeks to complete.

The script reads in information from a whole host of files, processes and outputs the information I need to text files, with a little bit of status information printed to the terminal. It seems to be running fine, and the output seems to be right. However, near the end of its processing of each text file, for some inexplicable reason, the script is dumping a wall of text onto the terminal:

The text seems to be memory addresses, but I have no idea why this might be happening. Should I be worried? Any help is much appreciated!

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EDIT: STDERR and STDOUT were being printed to text files. I combed through the outputs more carefully and there seems to be some missing information. I added close(STDERR) and close(STDOUT) to the script, to see if there was some sort printing error. The script now prints the following error *** buffer overflow detected ***: Perl terminated

Answer 1

Given the updated screen shot in your most recent edit, it appears there's a bug in an XS module overflowing a buffer, and that's what the stack backtrace is complaining about. You can see in the screen shot the backtrace:

/lib64/libc.so.6(__fortify_fail+0x37)[0x7fb026838637]
/lib64/libc.so.6(+0xf8690)[0x7fb026836690]
/home/ex2-user/j_authority/_Inline/lib/auto/author_da35/author_da35.so(profiles_c+0x27fd)[0x7fb008a529ad]
/home/ex2-user/j_authority/_Inline/lib/auto/author_da35/author_da35.so(XS_author_profiles_c+0x32a)[0x7fb008a55afa]

So, it appears you're in the middle of this XS module when Fortify detected a stack overflow. This suggests a function-local array to some function internal to author_da35 got overrun. This could happen if, for example, it sized some structure expecting 32-bit pointers, but you're running on a 64-bit machine. (Which, it appears you are.) Or, it could just be it allocated a fixed sized structure and your dataset needs something larger.

Looking around, some other classes of problems can trigger "buffer overflow," such as opening too many files, but that seems like a less likely circumstance.

In any case, it appears to be a bug in the module.

If you're not familiar with XS, the short description is that it's a mechanism that allows perl to call native-compiled code. Perl itself is interpreted, but its XS API allows you to interface perl code with compiled languages such as C or C++. A couple links if you're interested in XS:

• http://en.wikipedia.org/wiki/XS_%28Perl%29
• http://perldoc.perl.org/perlxs.html

As far as fixing your problem, you'll need to actually correct the C or C++ code in profiles_c in author_da35. Hopefully you're on good terms with the module's author. :-)

You can find out more about Fortify by googling FORTIFY_SOURCE.