module: don't modify argument of module_kallsyms_lookup_name()

If we pass a pointer to a const string in the form "module:symbol"
module_kallsyms_lookup_name() will try to split the string at the colon,
i.e., will try to modify r/o data. That will, in fact, fail on a kernel
with enabled CONFIG_DEBUG_RODATA.

Avoid modifying the passed string in module_kallsyms_lookup_name(),
modify find_module_all() instead to pass it the module name length.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

diff --git a/kernel/module.c b/kernel/module.c
index b049939..a1951ab 100644 (file)
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -455,7 +455,7 @@ const struct kernel_symbol *find_symbol(const char *name,
 EXPORT_SYMBOL_GPL(find_symbol);
 
 /* Search for module by name: must hold module_mutex. */
-static struct module *find_module_all(const char *name,
+static struct module *find_module_all(const char *name, size_t len,
                                      bool even_unformed)
 {
        struct module *mod;
@@ -463,7 +463,7 @@ static struct module *find_module_all(const char *name,
        list_for_each_entry(mod, &modules, list) {
                if (!even_unformed && mod->state == MODULE_STATE_UNFORMED)
                        continue;
-               if (strcmp(mod->name, name) == 0)
+               if (strlen(mod->name) == len && !memcmp(mod->name, name, len))
                        return mod;
        }
        return NULL;
@@ -471,7 +471,7 @@ static struct module *find_module_all(const char *name,
 
 struct module *find_module(const char *name)
 {
-       return find_module_all(name, false);
+       return find_module_all(name, strlen(name), false);
 }
 EXPORT_SYMBOL_GPL(find_module);
 
@@ -3027,7 +3027,7 @@ static bool finished_loading(const char *name)
        bool ret;
 
        mutex_lock(&module_mutex);
-       mod = find_module_all(name, true);
+       mod = find_module_all(name, strlen(name), true);
        ret = !mod || mod->state == MODULE_STATE_LIVE
                || mod->state == MODULE_STATE_GOING;
        mutex_unlock(&module_mutex);
@@ -3165,7 +3165,8 @@ static int add_unformed_module(struct module *mod)
 
 again:
        mutex_lock(&module_mutex);
-       if ((old = find_module_all(mod->name, true)) != NULL) {
+       old = find_module_all(mod->name, strlen(mod->name), true);
+       if (old != NULL) {
                if (old->state == MODULE_STATE_COMING
                    || old->state == MODULE_STATE_UNFORMED) {
                        /* Wait in case it fails to load. */
@@ -3576,10 +3577,8 @@ unsigned long module_kallsyms_lookup_name(const char *name)
        /* Don't lock: we're in enough trouble already. */
        preempt_disable();
        if ((colon = strchr(name, ':')) != NULL) {
-               *colon = '\0';
-               if ((mod = find_module(name)) != NULL)
+               if ((mod = find_module_all(name, colon - name, false)) != NULL)
                        ret = mod_find_symname(mod, colon+1);
-               *colon = ':';
        } else {
                list_for_each_entry_rcu(mod, &modules, list) {
                        if (mod->state == MODULE_STATE_UNFORMED)