[PATCH 4.14 26/89] af_key: fix buffer overread in parse_exthdrs()

[Greg Kroah-Hartman]

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

------------------

From: Eric Biggers <ebigg...@google.com>

commit 4e765b4972af7b07adcb1feb16e7a525ce1f6b28 upstream.

If a message sent to a PF_KEY socket ended with an incomplete extension
header (fewer than 4 bytes remaining), then parse_exthdrs() read past
the end of the message, into uninitialized memory.  Fix it by returning
-EINVAL in this case.

Reproducer:

        #include <linux/pfkeyv2.h>
        #include <sys/socket.h>
        #include <unistd.h>

        int main()
        {
                int sock = socket(PF_KEY, SOCK_RAW, PF_KEY_V2);
                char buf[17] = { 0 };
                struct sadb_msg *msg = (void *)buf;

                msg->sadb_msg_version = PF_KEY_V2;
                msg->sadb_msg_type = SADB_DELETE;
                msg->sadb_msg_len = 2;

                write(sock, buf, 17);
        }

Signed-off-by: Eric Biggers <ebigg...@google.com>
Signed-off-by: Steffen Klassert <steffen.klass...@secunet.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 net/key/af_key.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/net/key/af_key.c
+++ b/net/key/af_key.c
@@ -516,6 +516,9 @@ static int parse_exthdrs(struct sk_buff
                uint16_t ext_type;
                int ext_len;
 
+               if (len < sizeof(*ehdr))
+                       return -EINVAL;
+
                ext_len  = ehdr->sadb_ext_len;
                ext_len *= sizeof(uint64_t);
                ext_type = ehdr->sadb_ext_type;