[PATCH 4.19 14/44] block/bio: Do not zero user pages

[Greg Kroah-Hartman]

4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Keith Busch <keith.busch@xxxxxxxxx>

commit f55adad601c6a97c8c9628195453e0fb23b4a0ae upstream.

We don't need to zero fill the bio if not using kernel allocated pages.

Fixes: f3587d76da05 ("block: Clear kernel memory before copying to user") # v4.20-rc2
Reported-by: Todd Aiken <taiken@xxxxxxxxx>
Cc: Laurence Oberman <loberman@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Cc: Bart Van Assche <bvanassche@xxxxxxx>
Tested-by: Laurence Oberman <loberman@xxxxxxxxxx>
Signed-off-by: Keith Busch <keith.busch@xxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 block/bio.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/block/bio.c
+++ b/block/bio.c
@@ -1262,7 +1262,8 @@ struct bio *bio_copy_user_iov(struct req
 		if (ret)
 			goto cleanup;
 	} else {
-		zero_fill_bio(bio);
+		if (bmd->is_our_pages)
+			zero_fill_bio(bio);
 		iov_iter_advance(iter, bio->bi_iter.bi_size);
 	}