linux-kernel - [PATCH] brd: Refuse improperly aligned discard requests

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Date:	Wed,  4 Nov 2015 17:13:39 +0100
From:	Jan Kara <jack@...e.com>
To:	axboe@...nel.dk
Cc:	LKML <linux-kernel@...r.kernel.org>, linux-fsdevel@...r.kernel.org,
	Christoph Hellwig <hch@...radead.org>, Jan Kara <jack@...e.com>
Subject: [PATCH] brd: Refuse improperly aligned discard requests

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 <jack@...e.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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