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authorDavid Howells <dhowells@redhat.com>2012-10-20 01:19:29 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2012-10-19 17:30:40 -0700
commitcaabe240574aec05b2f5667414ce80f9075c2ba1 (patch)
treed92bf96b009bd0b0caec44c21348812b06805909 /kernel/module.c
parentb6bb324dbddd704b4b9a85971e1f7ae79abb2e1d (diff)
downloadlinaro-lsk-caabe240574aec05b2f5667414ce80f9075c2ba1.tar.gz
MODSIGN: Move the magic string to the end of a module and eliminate the search
Emit the magic string that indicates a module has a signature after the signature data instead of before it. This allows module_sig_check() to be made simpler and faster by the elimination of the search for the magic string. Instead we just need to do a single memcmp(). This works because at the end of the signature data there is the fixed-length signature information block. This block then falls immediately prior to the magic number. From the contents of the information block, it is trivial to calculate the size of the signature data and thus the size of the actual module data. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/module.c')
-rw-r--r--kernel/module.c26
1 files changed, 9 insertions, 17 deletions
diff --git a/kernel/module.c b/kernel/module.c
index 0e2da8695f8..6085f5ef88e 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2421,25 +2421,17 @@ static inline void kmemleak_load_module(const struct module *mod,
#ifdef CONFIG_MODULE_SIG
static int module_sig_check(struct load_info *info,
- const void *mod, unsigned long *len)
+ const void *mod, unsigned long *_len)
{
int err = -ENOKEY;
- const unsigned long markerlen = sizeof(MODULE_SIG_STRING) - 1;
- const void *p = mod, *end = mod + *len;
-
- /* Poor man's memmem. */
- while ((p = memchr(p, MODULE_SIG_STRING[0], end - p))) {
- if (p + markerlen > end)
- break;
-
- if (memcmp(p, MODULE_SIG_STRING, markerlen) == 0) {
- const void *sig = p + markerlen;
- /* Truncate module up to signature. */
- *len = p - mod;
- err = mod_verify_sig(mod, *len, sig, end - sig);
- break;
- }
- p++;
+ unsigned long markerlen = sizeof(MODULE_SIG_STRING) - 1;
+ unsigned long len = *_len;
+
+ if (len > markerlen &&
+ memcmp(mod + len - markerlen, MODULE_SIG_STRING, markerlen) == 0) {
+ /* We truncate the module to discard the signature */
+ *_len -= markerlen;
+ err = mod_verify_sig(mod, _len);
}
if (!err) {