1 files changed, 87 insertions, 5 deletions

diff --git a/net/dns_resolver/dns_key.c b/net/dns_resolver/dns_key.c
index 400a04d5c9a1..739435a6af39 100644
--- a/net/dns_resolver/dns_key.c
+++ b/net/dns_resolver/dns_key.c
@@ -29,6 +29,7 @@
 #include <linux/kernel.h>
 #include <linux/keyctl.h>
 #include <linux/err.h>
+#include <linux/seq_file.h>
 #include <keys/dns_resolver-type.h>
 #include <keys/user-type.h>
 #include "internal.h"
@@ -43,6 +44,8 @@ MODULE_PARM_DESC(debug, "DNS Resolver debugging mask");
 
 const struct cred *dns_resolver_cache;
 
+#define	DNS_ERRORNO_OPTION	"dnserror"
+
 /*
  * Instantiate a user defined key for dns_resolver.
  *
@@ -59,9 +62,10 @@ static int
 dns_resolver_instantiate(struct key *key, const void *_data, size_t datalen)
 {
 	struct user_key_payload *upayload;
+	unsigned long derrno;
 	int ret;
 	size_t result_len = 0;
-	const char *data = _data, *opt;
+	const char *data = _data, *end, *opt;
 
 	kenter("%%%d,%s,'%s',%zu",
 	       key->serial, key->description, data, datalen);
@@ -71,13 +75,77 @@ dns_resolver_instantiate(struct key *key, const void *_data, size_t datalen)
 	datalen--;
 
 	/* deal with any options embedded in the data */
+	end = data + datalen;
 	opt = memchr(data, '#', datalen);
 	if (!opt) {
-		kdebug("no options currently supported");
-		return -EINVAL;
+		/* no options: the entire data is the result */
+		kdebug("no options");
+		result_len = datalen;
+	} else {
+		const char *next_opt;
+
+		result_len = opt - data;
+		opt++;
+		kdebug("options: '%s'", opt);
+		do {
+			const char *eq;
+			int opt_len, opt_nlen, opt_vlen, tmp;
+
+			next_opt = memchr(opt, '#', end - opt) ?: end;
+			opt_len = next_opt - opt;
+			if (!opt_len) {
+				printk(KERN_WARNING
+				       "Empty option to dns_resolver key %d\n",
+				       key->serial);
+				return -EINVAL;
+			}
+
+			eq = memchr(opt, '=', opt_len) ?: end;
+			opt_nlen = eq - opt;
+			eq++;
+			opt_vlen = next_opt - eq; /* will be -1 if no value */
+
+			tmp = opt_vlen >= 0 ? opt_vlen : 0;
+			kdebug("option '%*.*s' val '%*.*s'",
+			       opt_nlen, opt_nlen, opt, tmp, tmp, eq);
+
+			/* see if it's an error number representing a DNS error
+			 * that's to be recorded as the result in this key */
+			if (opt_nlen == sizeof(DNS_ERRORNO_OPTION) - 1 &&
+			    memcmp(opt, DNS_ERRORNO_OPTION, opt_nlen) == 0) {
+				kdebug("dns error number option");
+				if (opt_vlen <= 0)
+					goto bad_option_value;
+
+				ret = strict_strtoul(eq, 10, &derrno);
+				if (ret < 0)
+					goto bad_option_value;
+
+				if (derrno < 1 || derrno > 511)
+					goto bad_option_value;
+
+				kdebug("dns error no. = %lu", derrno);
+				key->type_data.x[0] = -derrno;
+				continue;
+			}
+
+		bad_option_value:
+			printk(KERN_WARNING
+			       "Option '%*.*s' to dns_resolver key %d:"
+			       " bad/missing value\n",
+			       opt_nlen, opt_nlen, opt, key->serial);
+			return -EINVAL;
+		} while (opt = next_opt + 1, opt < end);
+	}
+
+	/* don't cache the result if we're caching an error saying there's no
+	 * result */
+	if (key->type_data.x[0]) {
+		kleave(" = 0 [h_error %ld]", key->type_data.x[0]);
+		return 0;
 	}
 
-	result_len = datalen;
+	kdebug("store result");
 	ret = key_payload_reserve(key, result_len);
 	if (ret < 0)
 		return -EINVAL;
@@ -135,13 +203,27 @@ no_match:
 	return ret;
 }
 
+/*
+ * Describe a DNS key
+ */
+static void dns_resolver_describe(const struct key *key, struct seq_file *m)
+{
+	int err = key->type_data.x[0];
+
+	seq_puts(m, key->description);
+	if (err)
+		seq_printf(m, ": %d", err);
+	else
+		seq_printf(m, ": %u", key->datalen);
+}
+
 struct key_type key_type_dns_resolver = {
 	.name		= "dns_resolver",
 	.instantiate	= dns_resolver_instantiate,
 	.match		= dns_resolver_match,
 	.revoke		= user_revoke,
 	.destroy	= user_destroy,
-	.describe	= user_describe,
+	.describe	= dns_resolver_describe,
 	.read		= user_read,
 };