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Posted to bugs@httpd.apache.org by bu...@apache.org on 2020/05/07 04:07:10 UTC
[Bug 64414] New: mod_ldap: High CPU usage at
apr_ldap_rebind_remove()
https://bz.apache.org/bugzilla/show_bug.cgi?id=64414
Bug ID: 64414
Summary: mod_ldap: High CPU usage at apr_ldap_rebind_remove()
Product: Apache httpd-2
Version: 2.4.43
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P2
Component: mod_ldap
Assignee: bugs@httpd.apache.org
Reporter: abhishekshah67@gmail.com
Target Milestone: ---
Description of problem:
In uldap_connection_unbind, apr_ldap_rebind_remove() is always passed
NULL since ldc->ldap is either NULL on entry or is set to NULL.
This thread is expensive as apr_ldap_rebind_remove() acquires a mutex and
iterates a linked list
trying to find a rebind reference matching NULL
~~~
173: while ((tmp_xref) && (tmp_xref->index != ld)) {
174: prev = tmp_xref;
175: tmp_xref = tmp_xref->next;
176: }
173 while ((tmp_xref) && (tmp_xref->index != ld)) {
**(gdb) p ld
$1 = (LDAP *) 0x0**
(gdb) p tmp_xref
$2 = (apr_ldap_rebind_entry_t *) 0x7f256418eea0
(gdb) p tmp_xref->index
$3 = (LDAP *) 0x7f254c00b2c0
(gdb) p tmp_xref->next
$4 = (struct apr_ldap_rebind_entry *) 0x7f256418eea0
(gdb) n
175 tmp_xref = tmp_xref->next;
(gdb) n
173 while ((tmp_xref) && (tmp_xref->index != ld)) {
(gdb) p tmp_xref
$5 = (apr_ldap_rebind_entry_t *) 0x7f256418eea0
(gdb)
~~~
http://svn.apache.org/viewvc/httpd/httpd/trunk/modules/ldap/util_ldap.c
~~~
static apr_status_t uldap_connection_unbind(void *param)
{
util_ldap_connection_t *ldc = param;
if (ldc) {
if (ldc->ldap) { # if not NULL
if (ldc->r) {
ap_log_rerror(APLOG_MARK, APLOG_TRACE5, 0, ldc->r, "LDC %pp
unbind", ldc);
}
ldap_unbind_s(ldc->ldap);
**ldc->ldap = NULL**; # Note the assignment
}
ldc->bound = 0;
/* forget the rebind info for this conn */
if (ldc->ChaseReferrals == AP_LDAP_CHASEREFERRALS_ON) { # if we get
into this block,
**apr_ldap_rebind_remove(ldc->ldap)**; # <--- Passes NULL always
apr_pool_clear(ldc->rebind_pool);
}
}
return APR_SUCCESS;
}
~~~
LDAPReferrals Off is a workaround to avoid this loop.
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[Bug 64414] mod_ldap: High CPU usage at apr_ldap_rebind_remove()
Posted by bu...@apache.org.
https://bz.apache.org/bugzilla/show_bug.cgi?id=64414
--- Comment #2 from Joe Orton <jo...@redhat.com> ---
WIP (and untested) patch https://github.com/apache/httpd/pull/124
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[Bug 64414] mod_ldap: High CPU usage at apr_ldap_rebind_remove()
Posted by bu...@apache.org.
https://bz.apache.org/bugzilla/show_bug.cgi?id=64414
Joe Orton <jo...@redhat.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution|--- |FIXED
--- Comment #3 from Joe Orton <jo...@redhat.com> ---
Fixed in r1878890
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[Bug 64414] mod_ldap: High CPU usage at apr_ldap_rebind_remove()
Posted by bu...@apache.org.
https://bz.apache.org/bugzilla/show_bug.cgi?id=64414
--- Comment #1 from Abhishek Sah <ab...@gmail.com> ---
Discussion thread: https://markmail.org/message/tbpxtc4emjgao7jp
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