[PATCH 6.1.y 1/2] tls: fix lockless read of strp->msg_ready in ->poll

[Artem Dinaburg <artem@trailofbits.com>]

From: Sabrina Dubroca <sd@queasysnail.net>

[ Upstream commit 0844370f8945086eb9335739d10205dcea8d707b ]

tls_sk_poll is called without locking the socket, and needs to read
strp->msg_ready (via tls_strp_msg_ready). Convert msg_ready to a bool
and use READ_ONCE/WRITE_ONCE where needed. The remaining reads are
only performed when the socket is locked.

Fixes: 121dca784fc0 ("tls: suppress wakeups unless we have a full record")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Link: https://lore.kernel.org/r/0b7ee062319037cf86af6b317b3d72f7bfcd2e97.1713797701.git.sd@queasysnail.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Assisted-by: Codex:GPT-5
Signed-off-by: Artem Dinaburg <artem@trailofbits.com>
---
Prerequisite for 2/2, applied verbatim with no source adaptation. This
also fixes a real lockless read of msg_ready in ->poll that 6.1.y has
on its own.

 include/net/tls.h  | 3 ++-
 net/tls/tls.h      | 2 +-
 net/tls/tls_strp.c | 6 +++---
 3 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/include/net/tls.h b/include/net/tls.h
index 037049def..b5856a280 100644
--- a/include/net/tls.h
+++ b/include/net/tls.h
@@ -122,7 +122,8 @@ struct tls_strparser {
 	u32 stopped : 1;
 	u32 copy_mode : 1;
 	u32 mixed_decrypted : 1;
-	u32 msg_ready : 1;
+
+	bool msg_ready;
 
 	struct strp_msg stm;
 
diff --git a/net/tls/tls.h b/net/tls/tls.h
index 8304afbe0..9fd5867a3 100644
--- a/net/tls/tls.h
+++ b/net/tls/tls.h
@@ -167,7 +167,7 @@ static inline struct sk_buff *tls_strp_msg(struct tls_sw_context_rx *ctx)
 
 static inline bool tls_strp_msg_ready(struct tls_sw_context_rx *ctx)
 {
-	return ctx->strp.msg_ready;
+	return READ_ONCE(ctx->strp.msg_ready);
 }
 
 static inline bool tls_strp_msg_mixed_decrypted(struct tls_sw_context_rx *ctx)
diff --git a/net/tls/tls_strp.c b/net/tls/tls_strp.c
index 850146ed2..32b57e574 100644
--- a/net/tls/tls_strp.c
+++ b/net/tls/tls_strp.c
@@ -366,7 +366,7 @@ static int tls_strp_copyin(read_descriptor_t *desc, struct sk_buff *in_skb,
 	if (strp->stm.full_len && strp->stm.full_len == skb->len) {
 		desc->count = 0;
 
-		strp->msg_ready = 1;
+		WRITE_ONCE(strp->msg_ready, 1);
 		tls_rx_msg_ready(strp);
 	}
 
@@ -533,7 +533,7 @@ static int tls_strp_read_sock(struct tls_strparser *strp)
 	if (!tls_strp_check_queue_ok(strp))
 		return tls_strp_read_copy(strp, false);
 
-	strp->msg_ready = 1;
+	WRITE_ONCE(strp->msg_ready, 1);
 	tls_rx_msg_ready(strp);
 
 	return 0;
@@ -585,7 +585,7 @@ void tls_strp_msg_done(struct tls_strparser *strp)
 	else
 		tls_strp_flush_anchor_copy(strp);
 
-	strp->msg_ready = 0;
+	WRITE_ONCE(strp->msg_ready, 0);
 	memset(&strp->stm, 0, sizeof(strp->stm));
 
 	tls_strp_check_rcv(strp);
-- 
2.43.0