tls: make sure to abort the stream if headers are bogus

[ Upstream commit 0aeb54a ]

Normally we wait for the socket to buffer up the whole record
before we service it. If the socket has a tiny buffer, however,
we read out the data sooner, to prevent connection stalls.
Make sure that we abort the connection when we find out late
that the record is actually invalid. Retrying the parsing is
fine in itself but since we copy some more data each time
before we parse we can overflow the allocated skb space.

Constructing a scenario in which we're under pressure without
enough data in the socket to parse the length upfront is quite
hard. syzbot figured out a way to do this by serving us the header
in small OOB sends, and then filling in the recvbuf with a large
normal send.

Make sure that tls_rx_msg_size() aborts strp, if we reach
an invalid record there's really no way to recover.

Reported-by: Lee Jones <lee@kernel.org>
Fixes: 84c61fe ("tls: rx: do not use the standard strparser")
Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Link: https://patch.msgid.link/20250917002814.1743558-1-kuba@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: kuba-moo

net/tls/tls.h

@@ -91,6 +91,7 @@ int tls_sk_query(struct sock *sk, int optname, char __user *optval,
 int tls_sk_attach(struct sock *sk, int optname, char __user *optval,
 		  unsigned int optlen);
 void tls_err_abort(struct sock *sk, int err);
+void tls_strp_abort_strp(struct tls_strparser *strp, int err);
 
 int tls_set_sw_offload(struct sock *sk, struct tls_context *ctx, int tx);
 void tls_update_rx_zc_capable(struct tls_context *tls_ctx);

net/tls/tls_strp.c

@@ -12,7 +12,7 @@
 
 static struct workqueue_struct *tls_strp_wq;
 
-static void tls_strp_abort_strp(struct tls_strparser *strp, int err)
+void tls_strp_abort_strp(struct tls_strparser *strp, int err)
 {
 	if (strp->stopped)
 		return;
@@ -210,11 +210,17 @@ static int tls_strp_copyin_frag(struct tls_strparser *strp, struct sk_buff *skb,
 				struct sk_buff *in_skb, unsigned int offset,
 				size_t in_len)
 {
+	unsigned int nfrag = skb->len / PAGE_SIZE;
 	size_t len, chunk;
 	skb_frag_t *frag;
 	int sz;
 
-	frag = &skb_shinfo(skb)->frags[skb->len / PAGE_SIZE];
+	if (unlikely(nfrag >= skb_shinfo(skb)->nr_frags)) {
+		DEBUG_NET_WARN_ON_ONCE(1);
+		return -EMSGSIZE;
+	}
+
+	frag = &skb_shinfo(skb)->frags[nfrag];
 
 	len = in_len;
 	/* First make sure we got the header */
@@ -515,10 +521,8 @@ static int tls_strp_read_sock(struct tls_strparser *strp)
 	tls_strp_load_anchor_with_queue(strp, inq);
 	if (!strp->stm.full_len) {
 		sz = tls_rx_msg_size(strp, strp->anchor);
-		if (sz < 0) {
-			tls_strp_abort_strp(strp, sz);
+		if (sz < 0)
 			return sz;
-		}
 
 		strp->stm.full_len = sz;
 

net/tls/tls_sw.c

@@ -2435,8 +2435,7 @@ int tls_rx_msg_size(struct tls_strparser *strp, struct sk_buff *skb)
 	return data_len + TLS_HEADER_SIZE;
 
 read_failure:
-	tls_err_abort(strp->sk, ret);
-
+	tls_strp_abort_strp(strp, ret);
 	return ret;
 }