modules: only allow symbol_get of EXPORT_SYMBOL_GPL modules

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>

diff --git a/kernel/module/main.c b/kernel/module/main.c
index 59b1d06..c395af9 100644 (file)
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -1295,12 +1295,20 @@ void *__symbol_get(const char *symbol)
        };
 
        preempt_disable();
-       if (!find_symbol(&fsa) || strong_try_module_get(fsa.owner)) {
-               preempt_enable();
-               return NULL;
+       if (!find_symbol(&fsa))
+               goto fail;
+       if (fsa.license != GPL_ONLY) {
+               pr_warn("failing symbol_get of non-GPLONLY symbol %s.\n",
+                       symbol);
+               goto fail;
        }
+       if (strong_try_module_get(fsa.owner))
+               goto fail;
        preempt_enable();
        return (void *)kernel_symbol_value(fsa.sym);
+fail:
+       preempt_enable();
+       return NULL;
 }
 EXPORT_SYMBOL_GPL(__symbol_get);