pg_ctl infinite loop and memory leak

Jeff Davis <pgsql@j-davis.com> writes:

I attached a quick patch that seems to do the trick. It appears that
fgets() will always return non-NULL if the size passed in is 1 (i.e.
maxlength in the caller is 0).

Huh, interesting corner case. I'd be inclined to fix by initializing
maxlength to 1 though.

Where's the memory leak?

regards, tom lane

On Tue, 2009-09-01 at 22:01 -0400, Tom Lane wrote:

Huh, interesting corner case. I'd be inclined to fix by initializing
maxlength to 1 though.

Where's the memory leak?

The xstrdup() on the zero-length string.

Regards,
Jeff Davis

Jeff Davis <pgsql@j-davis.com> writes:

On Tue, 2009-09-01 at 22:01 -0400, Tom Lane wrote:

Where's the memory leak?

The xstrdup() on the zero-length string.

Oh, I see. But actually, it's also clobbering memory like crazy (since
we'll run off the result[] array in no time). Surprising it doesn't
crash from that.

regards, tom lane

Jeff Davis wrote:

To reproduce:

1. initdb -D data
2. cat /dev/null > data/postgresql.conf
3. pg_ctl -w -D data start

I attached a quick patch that seems to do the trick. It appears that
fgets() will always return non-NULL if the size passed in is 1 (i.e.
maxlength in the caller is 0).

The patch also changes the same readfile() function in initdb.c. I
assume it's not a practical problem there, but it should be fixed.

Thanks to Corry Haines (chaines at truviso dot com) for reporting the
problem.

I thought I knew the libc API pretty well, but I learned something new
here. :-)

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Bruce Momjian <bruce@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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