Fix race between cat /proc/slab_allocators and rmmod

Same story as with cat /proc/*/wchan race vs rmmod race, only
/proc/slab_allocators want more info than just symbol name.

Signed-off-by: Alexey Dobriyan <adobriyan@sw.ru>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/module.c b/kernel/module.c
index 3da76ad..d36e454 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2149,6 +2149,33 @@
 	return -ERANGE;
 }
 
+int lookup_module_symbol_attrs(unsigned long addr, unsigned long *size,
+			unsigned long *offset, char *modname, char *name)
+{
+	struct module *mod;
+
+	mutex_lock(&module_mutex);
+	list_for_each_entry(mod, &modules, list) {
+		if (within(addr, mod->module_init, mod->init_size) ||
+		    within(addr, mod->module_core, mod->core_size)) {
+			const char *sym;
+
+			sym = get_ksymbol(mod, addr, size, offset);
+			if (!sym)
+				goto out;
+			if (modname)
+				strlcpy(modname, mod->name, MODULE_NAME_LEN + 1);
+			if (name)
+				strlcpy(name, sym, KSYM_NAME_LEN + 1);
+			mutex_unlock(&module_mutex);
+			return 0;
+		}
+	}
+out:
+	mutex_unlock(&module_mutex);
+	return -ERANGE;
+}
+
 int module_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
 			char *name, char *module_name, int *exported)
 {