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>

1 files changed, 7 insertions, 8 deletions

diff --git a/kernel/module.c b/kernel/module.c
index b049939177f6..a1951aba7a03 100644
--- 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)