[asterisk-dev] [Code Review] Make ast_unload_resource actually remove the module from the module list when it is unloaded

[wdoekes]

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I don't like it.

Correct me if I'm wrong, but you're removing it there, so it won't show up in this bit:

                AST_LIST_TRAVERSE_SAFE_BEGIN(&module_list, mod, entry) {
                        if (!final && mod->usecount) {
                                continue;
                        }
                        AST_LIST_REMOVE_CURRENT(entry);
                        if (mod->flags.running && !mod->flags.declined && mod->info->unload) {
                                mod->info->unload();
                        }
                        AST_LIST_HEAD_DESTROY(&mod->users);
                        free(mod);
                        somethingchanged = 1;
                }
                AST_LIST_TRAVERSE_SAFE_END;

But who does the free'ing of mod then? (As an aside, shouldn't that be ast_free() instead of free()?)

- wdoekes


On Feb. 18, 2012, 1:31 p.m., Terry Wilson wrote:
> 
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> https://reviewboard.asterisk.org/r/1752/
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> 
> (Updated Feb. 18, 2012, 1:31 p.m.)
> 
> 
> Review request for Asterisk Developers.
> 
> 
> Summary
> -------
> 
> res_calendar calls ast_unload_resource for the related tech modules when it is unloaded. If this happens through a 'core stop gracefully', then it will be unloading the tech modules that are already in the list that is being traversed (supposedly safely) for unloading, eventually causing a double free. The problem seems to be that ast_unload_resource, while it calls the unload() callback function for the module, does not actually unlink the module from the list of modules. So the AST_LIST_TRAVERSE_SAFE_BEGIN {} still iterates over the unloaded module.
> 
> This patch causes ast_unload_resource to call AST_LIST_REMOVE on successfully unloaded modules.
> 
> 
> Diffs
> -----
> 
>   /trunk/main/loader.c 355783 
> 
> Diff: https://reviewboard.asterisk.org/r/1752/diff
> 
> 
> Testing
> -------
> 
> Scenario: Start Asterisk with res_calendar and assorted calendar tech modules loaded. Run 'core stop gracefully'.
> Before patch: Crash.
> After patch: No crash.
> 
> 
> Thanks,
> 
> Terry
> 
>

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