netdev - [PATCH net-next v2] tls: Skip zerocopy path for ITER

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Message-ID: <20180725214821.1402538-1-doronrk@fb.com>
Date:   Wed, 25 Jul 2018 14:48:21 -0700
From:   Doron Roberts-Kedes <doronrk@...com>
To:     "David S . Miller" <davem@...emloft.net>
CC:     Dave Watson <davejwatson@...com>, <netdev@...r.kernel.org>,
        Doron Roberts-Kedes <doronrk@...com>
Subject: [PATCH net-next v2] tls: Skip zerocopy path for ITER_KVEC

The zerocopy path ultimately calls iov_iter_get_pages, which defines the
step function for ITER_KVECs as simply, return -EFAULT. Taking the
non-zerocopy path for ITER_KVECs avoids the unnecessary fallback.

See https://lore.kernel.org/lkml/20150401023311.GL29656@ZenIV.linux.org.uk/T/#u
for a discussion of why zerocopy for vmalloc data is not a good idea.

Discovered while testing NBD traffic encrypted with ktls.

Fixes: c46234ebb4d1 ("tls: RX path for ktls")
Signed-off-by: Doron Roberts-Kedes <doronrk@...com>
---
 net/tls/tls_sw.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index 1f3d9789af30..da584dc7d633 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -377,6 +377,7 @@ int tls_sw_sendmsg(struct sock *sk, struct msghdr *msg, size_t size)
 	int record_room;
 	bool full_record;
 	int orig_size;
+	bool is_kvec = msg->msg_iter.type & ITER_KVEC;
 
 	if (msg->msg_flags & ~(MSG_MORE | MSG_DONTWAIT | MSG_NOSIGNAL))
 		return -ENOTSUPP;
@@ -425,8 +426,7 @@ int tls_sw_sendmsg(struct sock *sk, struct msghdr *msg, size_t size)
 			try_to_copy -= required_size - ctx->sg_encrypted_size;
 			full_record = true;
 		}
-
-		if (full_record || eor) {
+		if (!is_kvec && (full_record || eor)) {
 			ret = zerocopy_from_iter(sk, &msg->msg_iter,
 				try_to_copy, &ctx->sg_plaintext_num_elem,
 				&ctx->sg_plaintext_size,
@@ -764,6 +764,7 @@ int tls_sw_recvmsg(struct sock *sk,
 	bool cmsg = false;
 	int target, err = 0;
 	long timeo;
+	bool is_kvec = msg->msg_iter.type & ITER_KVEC;
 
 	flags |= nonblock;
 
@@ -807,7 +808,7 @@ int tls_sw_recvmsg(struct sock *sk,
 			page_count = iov_iter_npages(&msg->msg_iter,
 						     MAX_SKB_FRAGS);
 			to_copy = rxm->full_len - tls_ctx->rx.overhead_size;
-			if (to_copy <= len && page_count < MAX_SKB_FRAGS &&
+			if (!is_kvec && to_copy <= len && page_count < MAX_SKB_FRAGS &&
 			    likely(!(flags & MSG_PEEK)))  {
 				struct scatterlist sgin[MAX_SKB_FRAGS + 1];
 				int pages = 0;
-- 
2.17.1