[PATCH v2 1/3] ublk: check import_ubuf() return value

[Caleb Sander Mateos]

import_ubuf() can fail if the address range (provided by the userspace
ublk server) is outside the allowed user address space. Return that 0
bytes were copied if import_ubuf() fails rather than passing an
uninitialized struct iov_iter to ublk_copy_user_pages().

Fixes: 981f95a571e3 ("ublk: cleanup ublk_copy_user_pages")
Reported-by: Ming Lei <tom.leiming@xxxxxxxxx>
Signed-off-by: Caleb Sander Mateos <csander@xxxxxxxxxxxxxxx>
---
 drivers/block/ublk_drv.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index 4ca6ec738c93..098e046505ad 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -1473,11 +1473,14 @@ static unsigned int ublk_map_io(const struct ublk_queue *ubq,
 	 */
 	if (ublk_need_map_req(req)) {
 		struct iov_iter iter;
 		const int dir = ITER_DEST;
 
-		import_ubuf(dir, u64_to_user_ptr(io->buf.addr), rq_bytes, &iter);
+		if (import_ubuf(dir, u64_to_user_ptr(io->buf.addr), rq_bytes,
+				&iter) < 0)
+			return 0;
+
 		return ublk_copy_user_pages(req, 0, &iter, dir);
 	}
 	return rq_bytes;
 }
 
@@ -1494,11 +1497,14 @@ static unsigned int ublk_unmap_io(bool need_map,
 		struct iov_iter iter;
 		const int dir = ITER_SOURCE;
 
 		WARN_ON_ONCE(io->res > rq_bytes);
 
-		import_ubuf(dir, u64_to_user_ptr(io->buf.addr), io->res, &iter);
+		if (import_ubuf(dir, u64_to_user_ptr(io->buf.addr), io->res,
+				&iter) < 0)
+			return 0;
+
 		return ublk_copy_user_pages(req, 0, &iter, dir);
 	}
 	return rq_bytes;
 }
 
-- 
2.54.0