Sent: 21 September 2020 15:34

Stop duplicating the iovec verify code, and instead add add a
__import_iovec helper that does the whole verify and import, but takes
a bool compat to decided on the native or compat layout.  This also
ends up massively simplifying the calling conventions.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 lib/iov_iter.c | 195 ++++++++++++++++++-------------------------------
 1 file changed, 70 insertions(+), 125 deletions(-)

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index a64867501a7483..8bfa47b63d39aa 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c

@@ -10,6 +10,7 @@
 #include <net/checksum.h>
 #include <linux/scatterlist.h>
 #include <linux/instrumented.h>
+#include <linux/compat.h>

 #define PIPE_PARANOIA /* for now */

@@ -1650,43 +1651,76 @@ const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags)
 }
 EXPORT_SYMBOL(dup_iter);

-static ssize_t rw_copy_check_uvector(int type,
-		const struct iovec __user *uvector, unsigned long nr_segs,
-		unsigned long fast_segs, struct iovec *fast_pointer,
-		struct iovec **ret_pointer)
+static int compat_copy_iovecs_from_user(struct iovec *iov,
+		const struct iovec __user *uvector, unsigned long nr_segs)
+{
+	const struct compat_iovec __user *uiov =
+		(const struct compat_iovec __user *)uvector;
+	unsigned long i;
+	int ret = -EFAULT;
+
+	if (!user_access_begin(uvector, nr_segs * sizeof(*uvector)))
+		return -EFAULT;