[PATCH 5/5] modules: only allow symbol_get of EXPORT_SYMBOL_GPL modules

From: Christoph Hellwig
Date: Tue Aug 01 2023 - 13:36:52 EST

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@xxxxxx>
Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
kernel/module/main.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/kernel/module/main.c b/kernel/module/main.c
index 59b1d067e52890..c395af9eced114 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -1295,12 +1295,20 @@ void *__symbol_get(const char *symbol)

- 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;
return (void *)kernel_symbol_value(fsa.sym);
+ preempt_enable();
+ return NULL;