keys, trusted: fix: *do not* allow duplicate key options

The trusted keys option parsing allows specifying the same option
multiple times. The last option value specified is used.

This is problematic because:

* No gain.
* This makes complicated to specify options that are dependent on other
  options.

This patch changes the behavior in a way that option can be specified
only once.
Reported-by: James Morris James Morris <jmorris@namei.org>
Reviewed-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Acked-by: Peter Huewe <peterhuewe@gmx.de>

security/keys/trusted.c

@@ -736,11 +736,14 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
 	int res;
 	unsigned long handle;
 	unsigned long lock;
+	unsigned long token_mask = 0;
 
 	while ((p = strsep(&c, " \t"))) {
 		if (*p == '\0' || *p == ' ' || *p == '\t')
 			continue;
 		token = match_token(p, key_tokens, args);
+		if (test_and_set_bit(token, &token_mask))
+			return -EINVAL;
 
 		switch (token) {
 		case Opt_pcrinfo: