[PATCH] Modules race fix

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Linus, please apply.

Name: Fix two module races
Author: Bob Miller, Rusty Russell
Status: Trivial

D: Bob Miller points out that the try_module_get in use_module() can,
D: of course, fail. Secondly, there is a race between setting the module
D: live, and a simultaneous removal of it.

diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.5.62-bk6/kernel/module.c working-2.5.62-bk6-modraces/kernel/module.c
--- linux-2.5.62-bk6/kernel/module.c 2003-02-18 11:18:57.000000000 +1100
+++ working-2.5.62-bk6-modraces/kernel/module.c 2003-02-24 13:42:44.000000000 +1100
@@ -173,16 +173,19 @@ static int use_module(struct module *a,
         struct module_use *use;
         if (b == NULL || already_uses(a, b)) return 1;
 
+ if (!strong_try_module_get(b))
+ 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 +1459,12 @@ sys_init_module(void *umod,
         }
 
         /* Now it's a first class citizen! */
+ down(&module_mutex);
         mod->state = MODULE_STATE_LIVE;
         module_free(mod, mod->module_init);
         mod->module_init = NULL;
         mod->init_size = 0;
+ up(&module_mutex);
 
         return 0;
 }

--
  Anyone who quotes me in their sig is an idiot. -- Rusty Russell.
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