From: Ben Hutchings <ben@decadent.org.uk>
Date: Wed, 27 Apr 2016 23:54:01 +0000 (+0930)
Subject: module: Invalidate signatures on force-loaded modules
X-Git-Tag: v3.14.77~2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fc77c4ad276a03ac9217e7db44339003ba1de6bd;p=thirdparty%2Fkernel%2Fstable.git

module: Invalidate signatures on force-loaded modules

commit bca014caaa6130e57f69b5bf527967aa8ee70fdd upstream.

Signing a module should only make it trusted by the specific kernel it
was built for, not anything else.  Loading a signed module meant for a
kernel with a different ABI could have interesting effects.
Therefore, treat all signatures as invalid when a module is
force-loaded.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/kernel/module.c b/kernel/module.c
index 3a311a1d26d7d..6113c5a536b8f 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2449,13 +2449,18 @@ static inline void kmemleak_load_module(const struct module *mod,
 #endif
 
 #ifdef CONFIG_MODULE_SIG
-static int module_sig_check(struct load_info *info)
+static int module_sig_check(struct load_info *info, int flags)
 {
 	int err = -ENOKEY;
 	const unsigned long markerlen = sizeof(MODULE_SIG_STRING) - 1;
 	const void *mod = info->hdr;
 
-	if (info->len > markerlen &&
+	/*
+	 * Require flags == 0, as a module with version information
+	 * removed is no longer the module that was signed
+	 */
+	if (flags == 0 &&
+	    info->len > markerlen &&
 	    memcmp(mod + info->len - markerlen, MODULE_SIG_STRING, markerlen) == 0) {
 		/* We truncate the module to discard the signature */
 		info->len -= markerlen;
@@ -2477,7 +2482,7 @@ static int module_sig_check(struct load_info *info)
 	return err;
 }
 #else /* !CONFIG_MODULE_SIG */
-static int module_sig_check(struct load_info *info)
+static int module_sig_check(struct load_info *info, int flags)
 {
 	return 0;
 }
@@ -3210,7 +3215,7 @@ static int load_module(struct load_info *info, const char __user *uargs,
 	struct module *mod;
 	long err;
 
-	err = module_sig_check(info);
+	err = module_sig_check(info, flags);
 	if (err)
 		goto free_copy;