From: Doron Roberts-Kedes <doronrk@fb.com>
Date: Thu, 26 Jul 2018 07:59:36 -0700
Subject: tls: Fix improper revert in zerocopy_from_iter
Patch-mainline: v4.19-rc1
Git-commit: 2da19ed3e4a87db16c0f69039da9f17a9596c350
References: bsc#1109837

The current code is problematic because the iov_iter is reverted and
never advanced in the non-error case. This patch skips the revert in the
non-error case. This patch also fixes the amount by which the iov_iter
is reverted. Currently, iov_iter is reverted by size, which can be
greater than the amount by which the iter was actually advanced.
Instead, only revert by the amount that the iter was advanced.

Fixes: 4718799817c5 ("tls: Fix zerocopy_from_iter iov handling")
Signed-off-by: Doron Roberts-Kedes <doronrk@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 net/tls/tls_sw.c |   12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -263,7 +263,7 @@ static int zerocopy_from_iter(struct soc
 			      int length, int *pages_used,
 			      unsigned int *size_used,
 			      struct scatterlist *to, int to_max_pages,
-			      bool charge, bool revert)
+			      bool charge)
 {
 	struct page *pages[MAX_SKB_FRAGS];
 
@@ -312,10 +312,10 @@ static int zerocopy_from_iter(struct soc
 	}
 
 out:
+	if (rc)
+		iov_iter_revert(from, size - *size_used);
 	*size_used = size;
 	*pages_used = num_elem;
-	if (revert)
-		iov_iter_revert(from, size);
 
 	return rc;
 }
@@ -417,7 +417,7 @@ alloc_encrypted:
 				&ctx->sg_plaintext_size,
 				ctx->sg_plaintext_data,
 				ARRAY_SIZE(ctx->sg_plaintext_data),
-				true, false);
+				true);
 			if (ret)
 				goto fallback_to_reg_send;
 
@@ -428,8 +428,6 @@ alloc_encrypted:
 			continue;
 
 fallback_to_reg_send:
-			iov_iter_revert(&msg->msg_iter,
-					ctx->sg_plaintext_size - orig_size);
 			trim_sg(sk, ctx->sg_plaintext_data,
 				&ctx->sg_plaintext_num_elem,
 				&ctx->sg_plaintext_size,
@@ -834,7 +832,7 @@ int tls_sw_recvmsg(struct sock *sk,
 				err = zerocopy_from_iter(sk, &msg->msg_iter,
 							 to_copy, &pages,
 							 &chunk, &sgin[1],
-							 MAX_SKB_FRAGS,	false, true);
+							 MAX_SKB_FRAGS,	false);
 				if (err < 0)
 					goto fallback_to_reg_recv;