modules: only allow symbol_get of EXPORT_SYMBOL_GPL modules

commit 9011e49d54dcc7653ebb8a1e05b5badb5ecfa9f9 upstream.

It has recently come to my attention that nvidia is circumventing the
protection added in 262e6ae7081d ("modules: inherit
TAINT_PROPRIETARY_MODULE") by importing exports from their proprietary
modules into an allegedly GPL licensed module and then rexporting them.

Given that symbol_get was only ever intended for tightly cooperating
modules using very internal symbols it is logical to restrict it to
being used on EXPORT_SYMBOL_GPL and prevent nvidia from costly DMCA
Circumvention of Access Controls law suites.

All symbols except for four used through symbol_get were already exported
as EXPORT_SYMBOL_GPL, and the remaining four ones were switched over in
the preparation patches.

Fixes: 262e6ae7081d ("modules: inherit TAINT_PROPRIETARY_MODULE")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/module.c b/kernel/module.c
index 2cd7de23cb1f0627355164d8d7ac7cd9d0eca94a..b9f582545b77ed0cc84303eeabc8ff9f66ea45b1 100644 (file)
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2227,15 +2227,26 @@ static void free_module(struct module *mod)
 void *__symbol_get(const char *symbol)
 {
        struct module *owner;
+       enum mod_license license;
        const struct kernel_symbol *sym;
 
        preempt_disable();
-       sym = find_symbol(symbol, &owner, NULL, NULL, true, true);
-       if (sym && strong_try_module_get(owner))
+       sym = find_symbol(symbol, &owner, NULL, &license, true, true);
+       if (!sym)
+               goto fail;
+       if (license != GPL_ONLY) {
+               pr_warn("failing symbol_get of non-GPLONLY symbol %s.\n",
+                       symbol);
+               goto fail;
+       }
+       if (strong_try_module_get(owner))
                sym = NULL;
        preempt_enable();
 
        return sym ? (void *)sym->value : NULL;
+fail:
+       preempt_enable();
+       return NULL;
 }
 EXPORT_SYMBOL_GPL(__symbol_get);