[PATCH 3.12 100/100] module: Invalidate signatures on force-loaded modules

[Jiri Slaby]

From: Ben Hutchings <b...@decadent.org.uk>

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

===============

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 <b...@decadent.org.uk>
Signed-off-by: Rusty Russell <ru...@rustcorp.com.au>
Signed-off-by: Jiri Slaby <jsl...@suse.cz>
---
 kernel/module.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/kernel/module.c b/kernel/module.c
index ec40f03aa473..a8c4d4163a41 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2491,13 +2491,18 @@ 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;
@@ -2519,7 +2524,7 @@ 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;
 }
@@ -3247,7 +3252,7 @@ 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;
 
-- 
2.9.3