mod_proxy/3178: Access Violation/SEGV in ap_proxy_cache_error

[Tim Costello <tj...@socs.uts.edu.au>]

>Number:         3178
>Category:       mod_proxy
>Synopsis:       Access Violation/SEGV in ap_proxy_cache_error
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    apache
>State:          open
>Class:          sw-bug
>Submitter-Id:   apache
>Arrival-Date:   Sat Oct 10 18:50:00 PDT 1998
>Last-Modified:
>Originator:     tjcostel@socs.uts.edu.au
>Organization:
apache
>Release:        1.3.3
>Environment:
Win NT 4.0 Intel, SP3
MS Visual C++ 5.0 SP3
>Description:
WinNT crashed before I could get a backtrace (!), but the function at fault was ap_proxy_cache_error.

It crashed because c->fp was a null pointer, ie c != NULL but c->fp == NULL.

This seems very similar to the case in PR2950. 

cache_req *ap_proxy_cache_error(cache_req *c)
{
    ap_log_rerror(APLOG_MARK, APLOG_ERR, c->req,
		 "proxy: error writing to cache file %s", c->tempfile);
/* CRASH ON NEXT LINE, c->fp == NULL */
    ap_pclosef(c->req->pool, c->fp->fd);
    c->fp = NULL;
    unlink(c->tempfile);
    return NULL;
}
>How-To-Repeat:
*Very* intermittent - only happens about every 50Mb of data that goes through the proxy
>Fix:
cache_req *ap_proxy_cache_error(cache_req *c)
{
    if (c != NULL) {
        ap_log_rerror(APLOG_MARK, APLOG_ERR, c->req,
		     "proxy: error writing to cache file %s", c->tempfile);
        if (c->fp != NULL) {
            ap_pclosef(c->req->pool, c->fp->fd);
            c->fp = NULL;
        }
        unlink(c->tempfile);
    }
    return NULL;
}
>Audit-Trail:
>Unformatted:
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