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From:   Christoph Hellwig <hch@lst.de>
To:     Jessica Yu <jeyu@kernel.org>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-kernel@vger.kernel.org (open list)
Subject: [PATCH 8/8] modules: inherit TAINT_PROPRIETARY_MODULE
Date:   Thu, 30 Jul 2020 08:10:27 +0200
Message-Id: <20200730061027.29472-9-hch@lst.de>
In-Reply-To: <20200730061027.29472-1-hch@lst.de>
References: <20200730061027.29472-1-hch@lst.de>
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If a TAINT_PROPRIETARY_MODULE exports symbol, inherit the taint flag
for all modules importing these symbols, and don't allow loading
symbols from TAINT_PROPRIETARY_MODULE modules if the module previously
imported gplonly symbols.  Add a anti-circumvention devices so people
don't accidentally get themselves into trouble this way.

Comment from Greg:
 Ah, the proven-to-be-illegal "GPL Condom" defense :)

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 include/linux/module.h |  1 +
 kernel/module.c        | 12 ++++++++++++
 2 files changed, 13 insertions(+)

diff --git a/include/linux/module.h b/include/linux/module.h
index 30b0f5fcdb3c37..e30ed5fa33a738 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -389,6 +389,7 @@ struct module {
 	unsigned int num_gpl_syms;
 	const struct kernel_symbol *gpl_syms;
 	const s32 *gpl_crcs;
+	bool using_gplonly_symbols;
 
 #ifdef CONFIG_UNUSED_SYMBOLS
 	/* unused exported symbols. */
diff --git a/kernel/module.c b/kernel/module.c
index afb2bfdd5134b3..04f993863ae417 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1456,6 +1456,18 @@ static const struct kernel_symbol *resolve_symbol(struct module *mod,
 	if (!sym)
 		goto unlock;
 
+	if (license == GPL_ONLY)
+		mod->using_gplonly_symbols = true;
+
+	if (owner && test_bit(TAINT_PROPRIETARY_MODULE, &owner->taints)) {
+		if (mod->using_gplonly_symbols) {
+			sym = NULL;
+			goto getname;
+		}
+		add_taint_module(mod, TAINT_PROPRIETARY_MODULE,
+				 LOCKDEP_NOW_UNRELIABLE);
+	}
+
 	if (!check_version(info, name, mod, crc)) {
 		sym = ERR_PTR(-EINVAL);
 		goto getname;
-- 
2.27.0