[PATCH 2/4] mm: make process_madvise() deal with ITER_UBUF

[Jens Axboe <axboe@kernel.dk>]

In preparation for having single segment iovec imports be transformed
into ITER_UBUF, ensure that process_madvise() deals with those correctly
when iterating the iov_iter.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 mm/madvise.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index 340125d08c03..2bd0f6c067bb 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -1503,7 +1503,12 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec,
 	total_len = iov_iter_count(&iter);
 
 	while (iov_iter_count(&iter)) {
-		iovec = iov_iter_iovec(&iter);
+		if (iter_is_ubuf(&iter)) {
+			iovec.iov_base = iter.ubuf + iter.iov_offset;
+			iovec.iov_len = iov_iter_count(&iter);
+		} else {
+			iovec = iov_iter_iovec(&iter);
+		}
 		ret = do_madvise(mm, (unsigned long)iovec.iov_base,
 					iovec.iov_len, behavior);
 		if (ret < 0)
-- 
2.39.2