Fix race between rmmod and cat /proc/kallsyms

module_get_kallsym() leaks "struct module *" outside of module_mutex which is
no-no, because module can dissapear right after mutex unlock.

Copy all needed information from inside module_mutex into caller-supplied
space.

[bunk@stusta.de: is_exported() can now become static]
Signed-off-by: Alexey Dobriyan <adobriyan@sw.ru>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 5 deletions

diff --git a/kernel/module.c b/kernel/module.c
index 43a529a1fa48..5ee65994a3bc 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1472,7 +1472,7 @@ static void setup_modinfo(struct module *mod, Elf_Shdr *sechdrs,
 }
 
 #ifdef CONFIG_KALLSYMS
-int is_exported(const char *name, const struct module *mod)
+static int is_exported(const char *name, const struct module *mod)
 {
         if (!mod && lookup_symbol(name, __start___ksymtab, __stop___ksymtab))
                 return 1;
@@ -2124,8 +2124,8 @@ const char *module_address_lookup(unsigned long addr,
         return NULL;
 }
 
-struct module *module_get_kallsym(unsigned int symnum, unsigned long *value,
-                                char *type, char *name)
+int module_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
+                        char *name, char *module_name, int *exported)
 {
         struct module *mod;
 
@@ -2136,13 +2136,15 @@ struct module *module_get_kallsym(unsigned int symnum, unsigned long *value,
                         *type = mod->symtab[symnum].st_info;
                         strlcpy(name, mod->strtab + mod->symtab[symnum].st_name,
                                 KSYM_NAME_LEN + 1);
+                        strlcpy(module_name, mod->name, MODULE_NAME_LEN + 1);
+                        *exported = is_exported(name, mod);
                         mutex_unlock(&module_mutex);
-                        return mod;
+                        return 0;
                 }
                 symnum -= mod->num_symtab;
         }
         mutex_unlock(&module_mutex);
-        return NULL;
+        return -ERANGE;
 }
 
 static unsigned long mod_find_symname(struct module *mod, const char *name)