From 357f435d8a0d32068c75f3c7176434d992b3adb7 Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Fri, 8 Apr 2016 19:05:19 -0400
Subject: [PATCH] fix the copy vs. map logics in blk_rq_map_user_iov()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 block/blk-map.c     | 47 ++++++++-------------------------------------
 include/linux/uio.h |  1 +
 lib/iov_iter.c      | 19 ++++++++++++++++++
 3 files changed, 28 insertions(+), 39 deletions(-)

diff --git a/block/blk-map.c b/block/blk-map.c
index a54f0543b956..b9f88b7751fb 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -9,24 +9,6 @@
 
 #include "blk.h"
 
-static bool iovec_gap_to_prv(struct request_queue *q,
-			     struct iovec *prv, struct iovec *cur)
-{
-	unsigned long prev_end;
-
-	if (!queue_virt_boundary(q))
-		return false;
-
-	if (prv->iov_base == NULL && prv->iov_len == 0)
-		/* prv is not set - don't check */
-		return false;
-
-	prev_end = (unsigned long)(prv->iov_base + prv->iov_len);
-
-	return (((unsigned long)cur->iov_base & queue_virt_boundary(q)) ||
-		prev_end & queue_virt_boundary(q));
-}
-
 int blk_rq_append_bio(struct request_queue *q, struct request *rq,
 		      struct bio *bio)
 {
@@ -125,31 +107,18 @@ int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
 			struct rq_map_data *map_data,
 			const struct iov_iter *iter, gfp_t gfp_mask)
 {
-	struct iovec iov, prv = {.iov_base = NULL, .iov_len = 0};
-	bool copy = (q->dma_pad_mask & iter->count) || map_data;
+	bool copy = false;
+	unsigned long align = q->dma_pad_mask | queue_dma_alignment(q);
 	struct bio *bio = NULL;
 	struct iov_iter i;
 	int ret;
 
-	if (!iter || !iter->count)
-		return -EINVAL;
-
-	iov_for_each(iov, i, *iter) {
-		unsigned long uaddr = (unsigned long) iov.iov_base;
-
-		if (!iov.iov_len)
-			return -EINVAL;
-
-		/*
-		 * Keep going so we check length of all segments
-		 */
-		if ((uaddr & queue_dma_alignment(q)) ||
-		    iovec_gap_to_prv(q, &prv, &iov))
-			copy = true;
-
-		prv.iov_base = iov.iov_base;
-		prv.iov_len = iov.iov_len;
-	}
+	if (map_data)
+		copy = true;
+	else if (iov_iter_alignment(iter) & align)
+		copy = true;
+	else if (queue_virt_boundary(q))
+		copy = queue_virt_boundary(q) & iov_iter_gap_alignment(iter);
 
 	i = *iter;
 	do {
diff --git a/include/linux/uio.h b/include/linux/uio.h
index fd9bcfedad42..1b5d1cd796e2 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -87,6 +87,7 @@ size_t copy_from_iter(void *addr, size_t bytes, struct iov_iter *i);
 size_t copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i);
 size_t iov_iter_zero(size_t bytes, struct iov_iter *);
 unsigned long iov_iter_alignment(const struct iov_iter *i);
+unsigned long iov_iter_gap_alignment(const struct iov_iter *i);
 void iov_iter_init(struct iov_iter *i, int direction, const struct iovec *iov,
 			unsigned long nr_segs, size_t count);
 void iov_iter_kvec(struct iov_iter *i, int direction, const struct kvec *kvec,
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 5fecddc32b1b..ca5316e0087b 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -569,6 +569,25 @@ unsigned long iov_iter_alignment(const struct iov_iter *i)
 }
 EXPORT_SYMBOL(iov_iter_alignment);
 
+unsigned long iov_iter_gap_alignment(const struct iov_iter *i)
+{
+        unsigned long res = 0;
+	size_t size = i->count;
+	if (!size)
+		return 0;
+
+	iterate_all_kinds(i, size, v,
+		(res |= (!res ? 0 : (unsigned long)v.iov_base) |
+			(size != v.iov_len ? size : 0), 0),
+		(res |= (!res ? 0 : (unsigned long)v.bv_offset) |
+			(size != v.bv_len ? size : 0)),
+		(res |= (!res ? 0 : (unsigned long)v.iov_base) |
+			(size != v.iov_len ? size : 0))
+		);
+		return res;
+}
+EXPORT_SYMBOL(iov_iter_gap_alignment);
+
 ssize_t iov_iter_get_pages(struct iov_iter *i,
 		   struct page **pages, size_t maxsize, unsigned maxpages,
 		   size_t *start)
-- 
2.20.1