From: | Alvaro Herrera <alvherre(at)commandprompt(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Sokolov Yura <funny(dot)falcon(at)gmail(dot)com>, pgsql-bugs(at)postgresql(dot)org, Peter Eisentraut <peter_e(at)gmx(dot)net>, Patches <pgsql-patches(at)postgresql(dot)org> |
Subject: | Re: BUG #3860: xpath crashes backend when is querying xmlagg result |
Date: | 2008-01-11 03:41:40 |
Message-ID: | 20080111034140.GV6465@alvh.no-ip.org |
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Lists: | pgsql-bugs pgsql-patches |
Tom Lane escribió:
> One thing I was wondering about earlier today is whether libxml isn't
> expecting NULL-return-on-failure from the malloc-substitute routine.
> If we take control away from it unexpectedly, I wouldn't be a bit
> surprised if its data structures are left corrupt. This might lead to
> failures during cleanup.
Hmm, this is a very good point. I quick look at the source shows that
they are not very consistent on its own checking for memory allocation
errors. For example, see a bug I just reported:
http://bugzilla.gnome.org/show_bug.cgi?id=508662
The problem is that many routines look like this:
xmlXPathNewNodeSet(xmlNodePtr val) {
xmlXPathObjectPtr ret;
ret = (xmlXPathObjectPtr) xmlMalloc(sizeof(xmlXPathObject));
if (ret == NULL) {
xmlXPathErrMemory(NULL, "creating nodeset\n");
return(NULL);
}
and others would call this code and then happily use the return value
without checking for null.
--
Alvaro Herrera http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support
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