Hi,
as an experiment to see if the segfault I am currently debugging were caused
by my modifications I found this. Httpd segfaults if its startup is aborted
because the DYNAMIC_MODULE_LIMIT is hit. The reason is that the module that
caused the abort is first unloaded as dso and then used in ap_remove_module as
ap_top_module. Unfortunately, the memory segment where the module is located
is already wiped from the process' address space at the time.
This happens because both apr_dso_load and mod_so:load_module register a pool
cleanup to undo their effects. These cleanup functions are called in the wrong
order.
I see 2 ways how to prevent that:
1) change in mod_so.c line 305 from
apr_pool_cleanup_register(cmd->pool, modi, unload_module,
apr_pool_cleanup_null);
to
apr_pool_pre_cleanup_register(cmd->pool, modi, unload_module);
This way ap_remove_module will be called before the dso is unloaded.
2) check for possible errors in ap_add_module() before performing any changes:
@@ -541,16 +565,11 @@
m->name, m->version, MODULE_MAGIC_NUMBER_MAJOR);
}
- if (m->next == NULL) {
- m->next = ap_top_module;
- ap_top_module = m;
- }
-
if (m->module_index == -1) {
m->module_index = total_modules++;
dynamic_modules++;
if (dynamic_modules > DYNAMIC_MODULE_LIMIT) {
return apr_psprintf(p, "Module \"%s\" could not be loaded, "
"because the dynamic module limit was "
"reached. Please increase "
@@ -568,6 +587,13 @@
}
}
+ if (m->next == NULL) {
+ m->next = ap_top_module;
+ ap_top_module = m;
+ }
+
if (sym_name) {
int len = strlen(sym_name);
int slen = strlen("_module");
Torsten Förtsch
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