[SRU][N][PATCH v2 1/1] tls: make sure to abort the stream if headers are bogus

[Tim Whisonant]

From: Jakub Kicinski <kuba at kernel.org>

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 at kernel.org>
Fixes: 84c61fe1a75b ("tls: rx: do not use the standard strparser")
Reviewed-by: Sabrina Dubroca <sd at queasysnail.net>
Signed-off-by: Jakub Kicinski <kuba at kernel.org>
Link: https://patch.msgid.link/20250917002814.1743558-1-kuba@kernel.org
Signed-off-by: Paolo Abeni <pabeni at redhat.com>
(cherry picked from commit 0aeb54ac4cd5cf8f60131b4d9ec0b6dc9c27b20d)
CVE-2025-39946
Signed-off-by: Tim Whisonant <tim.whisonant at canonical.com>
---
 net/tls/tls.h      |  1 +
 net/tls/tls_strp.c | 14 +++++++++-----
 net/tls/tls_sw.c   |  3 +--
 3 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/net/tls/tls.h b/net/tls/tls.h
index e5e47452308ab..d8fff03363c25 100644
--- a/net/tls/tls.h
+++ b/net/tls/tls.h
@@ -141,6 +141,7 @@ void update_sk_prot(struct sock *sk, struct tls_context *ctx);
 
 int wait_on_pending_writer(struct sock *sk, long *timeo);
 void tls_err_abort(struct sock *sk, int err);
+void tls_strp_abort_strp(struct tls_strparser *strp, int err);
 
 int init_prot_info(struct tls_prot_info *prot,
 		   const struct tls_crypto_info *crypto_info,
diff --git a/net/tls/tls_strp.c b/net/tls/tls_strp.c
index 5df08d848b5c9..d9d4352c728c1 100644
--- a/net/tls/tls_strp.c
+++ b/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 */
@@ -514,10 +520,8 @@ static int tls_strp_read_sock(struct tls_strparser *strp)
 		tls_strp_load_anchor_with_queue(strp, inq);
 
 		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;
 
diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index dc3756977a843..4b4857743ad50 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -2416,8 +2416,7 @@ 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;
 }
 
-- 
2.43.0