module: check kernel param length at compile time, not runtime

The kparam code tries to handle over-length parameter prefixes at
runtime.  Not only would I bet this has never been tested, it's not
clear that truncating names is a good idea either.

So let's check at compile time.  We need to move the #define to
moduleparam.h to do this, though.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

diff --git a/include/linux/module.h b/include/linux/module.h
index eddf27db442bf27d46845516dae2a6c85221e5a8..196b499270da1f585d1c700f7545d55e0c6380bb 100644 (file)
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -29,7 +29,7 @@
 #define MODULE_SYMBOL_PREFIX ""
 #endif
 
-#define MODULE_NAME_LEN (64 - sizeof(unsigned long))
+#define MODULE_NAME_LEN MAX_PARAM_PREFIX_LEN
 
 struct kernel_symbol
 {

diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h
index ec624381c844e26db58bbdd94eeee9e0b9de6962..1eefe6d61b86f6822f92610ad2acfe6d2b366863 100644 (file)
--- a/include/linux/moduleparam.h
+++ b/include/linux/moduleparam.h
@@ -13,6 +13,9 @@
 #define MODULE_PARAM_PREFIX KBUILD_MODNAME "."
 #endif
 
+/* Chosen so that structs with an unsigned long line up. */
+#define MAX_PARAM_PREFIX_LEN (64 - sizeof(unsigned long))
+
 #ifdef MODULE
 #define ___module_cat(a,b) __mod_ ## a ## b
 #define __module_cat(a,b) ___module_cat(a,b)
@@ -79,7 +82,8 @@ struct kparam_array
 #define __module_param_call(prefix, name, set, get, arg, perm)         \
        /* Default value instead of permissions? */                     \
        static int __param_perm_check_##name __attribute__((unused)) =  \
-       BUILD_BUG_ON_ZERO((perm) < 0 || (perm) > 0777 || ((perm) & 2)); \
+       BUILD_BUG_ON_ZERO((perm) < 0 || (perm) > 0777 || ((perm) & 2))  \
+       + BUILD_BUG_ON_ZERO(sizeof(""prefix) > MAX_PARAM_PREFIX_LEN);   \
        static const char __param_str_##name[] = prefix #name;          \
        static struct kernel_param __moduleparam_const __param_##name   \
        __used                                                          \

diff --git a/kernel/params.c b/kernel/params.c
index afc46a23eb6d15ebfb328f242979d75998d6d4c4..aca07e1a050f651c34cacacb8c37a4755ddb60ab 100644 (file)
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -585,17 +585,14 @@ static void __init param_sysfs_builtin(void)
 {
        struct kernel_param *kp, *kp_begin = NULL;
        unsigned int i, name_len, count = 0;
-       char modname[MODULE_NAME_LEN + 1] = "";
+       char modname[MODULE_NAME_LEN] = "";
 
        for (i=0; i < __stop___param - __start___param; i++) {
                char *dot;
-               size_t max_name_len;
 
                kp = &__start___param[i];
-               max_name_len =
-                       min_t(size_t, MODULE_NAME_LEN, strlen(kp->name));
 
-               dot = memchr(kp->name, '.', max_name_len);
+               dot = strchr(kp->name, '.');
                if (!dot) {
                        DEBUGP("couldn't find period in first %d characters "
                               "of %s\n", MODULE_NAME_LEN, kp->name);