Re: [xml] stack corruption (2.5.4)

[Gary Pennington sun com]

On Wed, Apr 30, 2003 at 03:55:43PM +0100, Gary Pennington sun com wrote:
> Ok, we've got a reproducible test case and I have some information.
> 
> If we apply the patch you sent out, then the stack corruption problem
> disappears but we get a core dump when the document is freed.
> 
> This problem is caused by the following line in the patch:
> 
> 	ret->doc = NULL;
> 
> This will set the external subset of the document to have a null pointer.
> 
> In xmlUnlinkNode(), the following line causes the SIGSEGV:
> 
>     if (cur->type == XML_DTD_NODE) {
> 	xmlDocPtr doc;
> 	doc = cur->doc;
> 	if (doc->intSubset == (xmlDtdPtr) cur)
>             doc->intSubset = NULL;
> 	 if (doc->extSubset == (xmlDtdPtr) cur) <== SIGSEGV HERE

Oops, I of course meant SIGSEGV on the above line.

Apologies,

Gary

> 	doc->extSubset = NULL;
>     }
> 
> The problem is that the document has an external subset associated with it
> but the external subset has had it's document reference removed.
> 
> My workaround is to take out the "ret->doc = NULL" line from the patch
> that Daniel submitted. This allows the application to complete normally.
> 
> However, I can't honestly say that this is the definitively correct answer,
> since I don't know why Daniel was setting this to NULL in his patch. It may
> be that it should be set to NULL and a check added to xmlUnlinkNode() to
> make sure that doc isn't NULL.
> 
> Is the above information enough to determine the correct answer?
> 
> Gary
> 
> On Wed, Apr 30, 2003 at 01:07:46PM +0100, Gary Pennington sun com wrote:
> > Thanks for the information. I'll try and identify a reproducible test case
> > and ensure that the patch fixes the problem.
> > 
> > It may take some time.
> > 
> > Gary
> > 
> > On Wed, Apr 30, 2003 at 06:49:42AM -0400, Daniel Veillard wrote:
> > > On Wed, Apr 30, 2003 at 12:47:40PM +0200, Petr Pajas wrote:
> > > > Gary Pennington sun com writes:
> > > > 
> > > > [snip]
> > > > > I am building a document in memory. Since I want to be able to access
> > > > > DTD information as I build my document, I do the following:
> > > > [snip]
> > > > > 		info.ktx_doc->extSubset =
> > > > > 		    xmlParseDTD(info.ktx_doc->intSubset->ExternalID,
> > > > > 			info.ktx_doc->intSubset->SystemID);
> > > > [snip]
> > > > > My questions are:
> > > > >
> > > > > 1. Is this a known problem in 2.5.4?
> > > > > 2. If so, will an upgrade to 2.5.7 fix it?
> > > > 
> > > > A bug in xmlParseDTD fixed by Daniel few days ago is very likely the
> > > > cause of the behavior you describe. Try upgrading from the CVS (or
> > > > wait for 2.5.8; 2.5.7 still contains the bug).
> > > 
> > >   Hum, right, I forgot about this, it's easy to check, the patch was
> > > enclosed in my answer.
> > > 
> > > Daniel
> > > 
> > > -- 
> > > Daniel Veillard      | Red Hat Network https://rhn.redhat.com/
> > > veillard redhat com  | libxml GNOME XML XSLT toolkit  http://xmlsoft.org/
> > > http://veillard.com/ | Rpmfind RPM search engine http://rpmfind.net/
> > _______________________________________________
> > xml mailing list, project page  http://xmlsoft.org/
> > xml gnome org
> > http://mail.gnome.org/mailman/listinfo/xml
> 
> -- 
> Gary Pennington
> Solaris Kernel Development,
> Sun Microsystems
> Gary Pennington sun com
> _______________________________________________
> xml mailing list, project page  http://xmlsoft.org/
> xml gnome org
> http://mail.gnome.org/mailman/listinfo/xml

-- 
Gary Pennington
Solaris Kernel Development,
Sun Microsystems
Gary Pennington sun com