Currently when improperly aligned discard request is submitted, we just
silently discard more / less data which results in filesystem corruption
in some cases. Refuse such misaligned requests.

Signed-off-by: Jan Kara <j...@suse.com>
---
 drivers/block/brd.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index b9794aeeb878..4ef4cdf67ede 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -337,6 +337,9 @@ static void brd_make_request(struct request_queue *q, 
struct bio *bio)
                goto io_error;
 
        if (unlikely(bio->bi_rw & REQ_DISCARD)) {
+               if (sector & ((PAGE_SIZE >> SECTOR_SHIFT) - 1) ||
+                   bio->bi_iter.bi_size & PAGE_MASK)
+                       goto io_error;
                discard_from_brd(brd, sector, bio->bi_iter.bi_size);
                goto out;
        }
-- 
2.1.4

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