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Subject[PATCH] Modules race fix
Date
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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