[PATCH 04/11] af_key: fix buffer overread in parse_exthdrs()

[Steffen Klassert]

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

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);
        }

Cc: sta...@vger.kernel.org
Signed-off-by: Eric Biggers <ebigg...@google.com>
Signed-off-by: Steffen Klassert <steffen.klass...@secunet.com>
---
 net/key/af_key.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/key/af_key.c b/net/key/af_key.c
index 596499cc8b2f..d40861a048fe 100644
--- a/net/key/af_key.c
+++ b/net/key/af_key.c
@@ -516,6 +516,9 @@ static int parse_exthdrs(struct sk_buff *skb, const struct 
sadb_msg *hdr, void *
                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;
-- 
2.14.1