Messages in this thread Patch in this message | | | Date | Fri, 21 Feb 2003 16:10:12 -0800 | From | Bob Miller <> | Subject | [PATCH 2.5.62] Fix two races in module code. |
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This patch fixes two bugs.
The first is that use_module() was ignoring the return value of try_module_get(). This causes an OOPs if a module needs symbols from a module that is halfway unloaded. The fix is to not ignore the error.
The second is a race in sys_init_module(). There is code at the bottom that changes the modules state from COMING to LIVE. After the LIVE is set it is possible for another thread to unload the module making the mod pointer used for the next few statements invalid. It would take a lot of interrupts or preempt but it could happen.
-- Bob Miller Email: rem@osdl.org Open Source Development Lab Phone: 503.626.2455 Ext. 17
diff -Nru a/kernel/module.c b/kernel/module.c --- a/kernel/module.c Fri Feb 21 15:57:53 2003 +++ b/kernel/module.c Fri Feb 21 15:57:53 2003 @@ -173,16 +173,22 @@ struct module_use *use; if (b == NULL || already_uses(a, b)) return 1; + /* + * If the module is being unloaded don't attach. + */ + if (try_module_get(b) == 0) { + return 0; + } DEBUGP("Allocating new usage for %s.\n", a->name); use = kmalloc(sizeof(*use), GFP_ATOMIC); if (!use) { printk("%s: out of memory loading\n", a->name); + module_put(b); return 0; } use->module_which_uses = a; list_add(&use->list, &b->modules_which_use_me); - try_module_get(b); /* Can't fail */ return 1; } @@ -1456,10 +1462,15 @@ } /* Now it's a first class citizen! */ - mod->state = MODULE_STATE_LIVE; module_free(mod, mod->module_init); mod->module_init = NULL; mod->init_size = 0; + /* + * Hold off setting state to "LIVE" until now. If set any + * sooner there is a race with an unload making the mod + * pointer invalid. + */ + mod->state = MODULE_STATE_LIVE; return 0; } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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