keys, dns: Fix size check of V1 server-list header

Fix the size check added to dns_resolver_preparse() for the V1 server-list
header so that it doesn't give EINVAL if the size supplied is the same as
the size of the header struct (which should be valid).

This can be tested with:

        echo -n -e '\0\0\01\xff\0\0' | keyctl padd dns_resolver desc @p

which will give "add_key: Invalid argument" without this fix.

Fixes: 1997b3cb4217 ("keys, dns: Fix missing size check of V1 server-list header")
Reported-by: Pengfei Xu <pengfei.xu@intel.com>
Link: https://lore.kernel.org/r/ZZ4fyY4r3rqgZL+4@xpf.sh.intel.com/
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/net/dns_resolver/dns_key.c b/net/dns_resolver/dns_key.c
index f18ca02aa95a61d3b16da500aa1df5362806de3a..c42ddd85ff1f9c3613b015c576b0ef458075d28e 100644 (file)
--- a/net/dns_resolver/dns_key.c
+++ b/net/dns_resolver/dns_key.c
@@ -104,7 +104,7 @@ dns_resolver_preparse(struct key_preparsed_payload *prep)
                const struct dns_server_list_v1_header *v1;
 
                /* It may be a server list. */
-               if (datalen <= sizeof(*v1))
+               if (datalen < sizeof(*v1))
                        return -EINVAL;
 
                v1 = (const struct dns_server_list_v1_header *)data;