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@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 3 deletions

diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index 0687a7a4689f..f9971717f7e0 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -362,6 +362,7 @@ 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;
@@ -410,8 +411,7 @@ alloc_encrypted:
                         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,
@@ -779,6 +779,7 @@ 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;
 
@@ -822,7 +823,7 @@ 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;