[PATCH 6.1 274/609] mac802154: llsec: reject frames shorter than the authentication tag

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

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

From: Doruk Tan Ozturk <[email protected]>

commit fd3a3f28ed60c6af4b2a39933b151d6b27842c3b upstream.

llsec_do_decrypt_auth() computes the associated-data length for the
AEAD request as

	assoclen += datalen - authlen;

where datalen is the number of bytes after the MAC header and authlen
(4, 8 or 16) is the length of the authentication tag. Nothing verifies
that the frame actually carries at least authlen payload bytes. A
secured frame whose payload is shorter than the tag makes
datalen - authlen negative; assoclen is then passed to
aead_request_set_ad() as an unsigned value close to 4 GiB, so
crypto_aead_decrypt() walks far off the end of the scatterlist that
only spans the real frame.

The frame is fully attacker-controlled and reaches this path from any
IEEE 802.15.4 peer in radio range. Reject frames whose payload is
shorter than the authentication tag before the subtraction.

Dynamically reproduced on a KASAN kernel as a general-protection-fault
in the AEAD scatterwalk, and the fix confirmed.

Fixes: 4c14a2fb5d14 ("mac802154: add llsec decryption method")
Cc: [email protected]
Reviewed-by: Simon Horman <[email protected]>
Signed-off-by: Doruk Tan Ozturk <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
 net/mac802154/llsec.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/net/mac802154/llsec.c
+++ b/net/mac802154/llsec.c
@@ -888,6 +888,11 @@ llsec_do_decrypt_auth(struct sk_buff *sk
 	data = skb_mac_header(skb) + skb->mac_len;
 	datalen = skb_tail_pointer(skb) - data;
 
+	if (datalen < authlen) {
+		kfree_sensitive(req);
+		return -EBADMSG;
+	}
+
 	sg_init_one(&sg, skb_mac_header(skb), assoclen + datalen);
 
 	if (!(hdr->sec.level & IEEE802154_SCF_SECLEVEL_ENC)) {