[SRU][N/P][PATCH v2 1/1] tls: handle data disappearing from under the TLS ULP

[Tim Whisonant]

From: Jakub Kicinski <kuba at kernel.org>

TLS expects that it owns the receive queue of the TCP socket.
This cannot be guaranteed in case the reader of the TCP socket
entered before the TLS ULP was installed, or uses some non-standard
read API (eg. zerocopy ones). Replace the WARN_ON() and a buggy
early exit (which leaves anchor pointing to a freed skb) with real
error handling. Wipe the parsing state and tell the reader to retry.

We already reload the anchor every time we (re)acquire the socket lock,
so the only condition we need to avoid is an out of bounds read
(not having enough bytes in the socket for previously parsed record len).

If some data was read from under TLS but there's enough in the queue
we'll reload and decrypt what is most likely not a valid TLS record.
Leading to some undefined behavior from TLS perspective (corrupting
a stream? missing an alert? missing an attack?) but no kernel crash
should take place.

Reported-by: William Liu <will at willsroot.io>
Reported-by: Savino Dicanosa <savy at syst3mfailure.io>
Link: https://lore.kernel.org/tFjq_kf7sWIG3A7CrCg_egb8CVsT_gsmHAK0_wxDPJXfIzxFAMxqmLwp3MlU5EHiet0AwwJldaaFdgyHpeIUCS-3m3llsmRzp9xIOBR4lAI=@syst3mfailure.io
Fixes: 84c61fe1a75b ("tls: rx: do not use the standard strparser")
Reviewed-by: Eric Dumazet <edumazet at google.com>
Link: https://patch.msgid.link/20250807232907.600366-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba at kernel.org>
(cherry picked from commit 6db015fc4b5d5f63a64a193f65d98da3a7fc811d)
CVE-2025-38616
Signed-off-by: Tim Whisonant <tim.whisonant at canonical.com>
---
 net/tls/tls.h      |  2 +-
 net/tls/tls_strp.c | 11 ++++++++---
 net/tls/tls_sw.c   |  3 ++-
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/net/tls/tls.h b/net/tls/tls.h
index e5e47452308ab..e1eaf12b37426 100644
--- a/net/tls/tls.h
+++ b/net/tls/tls.h
@@ -195,7 +195,7 @@ void tls_strp_msg_done(struct tls_strparser *strp);
 int tls_rx_msg_size(struct tls_strparser *strp, struct sk_buff *skb);
 void tls_rx_msg_ready(struct tls_strparser *strp);
 
-void tls_strp_msg_load(struct tls_strparser *strp, bool force_refresh);
+bool tls_strp_msg_load(struct tls_strparser *strp, bool force_refresh);
 int tls_strp_msg_cow(struct tls_sw_context_rx *ctx);
 struct sk_buff *tls_strp_msg_detach(struct tls_sw_context_rx *ctx);
 int tls_strp_msg_hold(struct tls_strparser *strp, struct sk_buff_head *dst);
diff --git a/net/tls/tls_strp.c b/net/tls/tls_strp.c
index 5df08d848b5c9..88906d51d37ed 100644
--- a/net/tls/tls_strp.c
+++ b/net/tls/tls_strp.c
@@ -473,7 +473,7 @@ static void tls_strp_load_anchor_with_queue(struct tls_strparser *strp, int len)
 	strp->stm.offset = offset;
 }
 
-void tls_strp_msg_load(struct tls_strparser *strp, bool force_refresh)
+bool tls_strp_msg_load(struct tls_strparser *strp, bool force_refresh)
 {
 	struct strp_msg *rxm;
 	struct tls_msg *tlm;
@@ -482,8 +482,11 @@ void tls_strp_msg_load(struct tls_strparser *strp, bool force_refresh)
 	DEBUG_NET_WARN_ON_ONCE(!strp->stm.full_len);
 
 	if (!strp->copy_mode && force_refresh) {
-		if (WARN_ON(tcp_inq(strp->sk) < strp->stm.full_len))
-			return;
+		if (unlikely(tcp_inq(strp->sk) < strp->stm.full_len)) {
+			WRITE_ONCE(strp->msg_ready, 0);
+			memset(&strp->stm, 0, sizeof(strp->stm));
+			return false;
+		}
 
 		tls_strp_load_anchor_with_queue(strp, strp->stm.full_len);
 	}
@@ -493,6 +496,8 @@ void tls_strp_msg_load(struct tls_strparser *strp, bool force_refresh)
 	rxm->offset	= strp->stm.offset;
 	tlm = tls_msg(strp->anchor);
 	tlm->control	= strp->mark;
+
+	return true;
 }
 
 /* Called with lock held on lower socket */
diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index 52de59b52e451..ae6268bbd01be 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -1356,7 +1356,8 @@ tls_rx_rec_wait(struct sock *sk, struct sk_psock *psock, bool nonblock,
 			return sock_intr_errno(timeo);
 	}
 
-	tls_strp_msg_load(&ctx->strp, released);
+	if (unlikely(!tls_strp_msg_load(&ctx->strp, released)))
+		return tls_rx_rec_wait(sk, psock, nonblock, false);
 
 	return 1;
 }
-- 
2.43.0