[PATCH 4.19 005/273] modules: only allow symbol_get of EXPORT_SYMBOL_GPL modules

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4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Christoph Hellwig <hch@xxxxxx>

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@xxxxxx>
Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 kernel/module.c |   15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2261,15 +2261,26 @@ static void free_module(struct module *m
 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 *)kernel_symbol_value(sym) : NULL;
+fail:
+	preempt_enable();
+	return NULL;
 }
 EXPORT_SYMBOL_GPL(__symbol_get);
 





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