[RFC / RFT net 3/7] tls: rx: strp: force mixed decrypted records into copy mode

[Jakub Kicinski <kuba@kernel.org>]

If a record is partially decrypted we'll have to CoW it, anyway,
so go into copy mode and allocate a writable skb right away.

This will make subsequent fix simpler because we won't have to
teach tls_strp_msg_make_copy() how to copy skbs while preserving
decrypt status.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 include/linux/skbuff.h | 10 ++++++++++
 net/tls/tls_strp.c     | 16 +++++++++++-----
 2 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 738776ab8838..0b40417457cd 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1587,6 +1587,16 @@ static inline void skb_copy_hash(struct sk_buff *to, const struct sk_buff *from)
 	to->l4_hash = from->l4_hash;
 };
 
+static inline int skb_cmp_decrypted(const struct sk_buff *skb1,
+				    const struct sk_buff *skb2)
+{
+#ifdef CONFIG_TLS_DEVICE
+	return skb2->decrypted - skb1->decrypted;
+#else
+	return 0;
+#endif
+}
+
 static inline void skb_copy_decrypted(struct sk_buff *to,
 				      const struct sk_buff *from)
 {
diff --git a/net/tls/tls_strp.c b/net/tls/tls_strp.c
index 90b220d1145c..9a125c28da88 100644
--- a/net/tls/tls_strp.c
+++ b/net/tls/tls_strp.c
@@ -317,15 +317,19 @@ static int tls_strp_read_copy(struct tls_strparser *strp, bool qshort)
 	return 0;
 }
 
-static bool tls_strp_check_no_dup(struct tls_strparser *strp)
+static bool tls_strp_check_queue_ok(struct tls_strparser *strp)
 {
 	unsigned int len = strp->stm.offset + strp->stm.full_len;
-	struct sk_buff *skb;
+	struct sk_buff *first, *skb;
 	u32 seq;
 
-	skb = skb_shinfo(strp->anchor)->frag_list;
-	seq = TCP_SKB_CB(skb)->seq;
+	first = skb_shinfo(strp->anchor)->frag_list;
+	skb = first;
+	seq = TCP_SKB_CB(first)->seq;
 
+	/* Make sure there's no duplicate data in the queue,
+	 * and the decrypted status matches.
+	 */
 	while (skb->len < len) {
 		seq += skb->len;
 		len -= skb->len;
@@ -333,6 +337,8 @@ static bool tls_strp_check_no_dup(struct tls_strparser *strp)
 
 		if (TCP_SKB_CB(skb)->seq != seq)
 			return false;
+		if (skb_cmp_decrypted(first, skb))
+			return false;
 	}
 
 	return true;
@@ -413,7 +419,7 @@ static int tls_strp_read_sock(struct tls_strparser *strp)
 			return tls_strp_read_copy(strp, true);
 	}
 
-	if (!tls_strp_check_no_dup(strp))
+	if (!tls_strp_check_queue_ok(strp))
 		return tls_strp_read_copy(strp, false);
 
 	strp->msg_ready = 1;
-- 
2.40.1