linux-kernel - [PATCH] block: avoid null pointer dereference on null disk

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Message-Id: <20171106175353.20199-1-colin.king@canonical.com>
Date:   Mon,  6 Nov 2017 17:53:53 +0000
From:   Colin King <colin.king@...onical.com>
To:     Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] block: avoid null pointer dereference on null disk

From: Colin Ian King <colin.king@...onical.com>

It is possible that the pointer disk can be null and hence
we can get a null pointer deference when accessing disk->flags.
Add a null pointer check to avoid the dereference.

Detected by CoverityScan, CID#1461133 ("Explicit null dereferenced")

Fixes: 8ddcd653257c ("block: introduce GENHD_FL_HIDDEN")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 block/genhd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/genhd.c b/block/genhd.c
index d85dcc701d76..42908a7186cd 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -798,7 +798,7 @@ struct gendisk *get_gendisk(dev_t devt, int *partno)
 		spin_unlock_bh(&ext_devt_lock);
 	}
 
-	if (unlikely(disk->flags & GENHD_FL_HIDDEN)) {
+	if (disk && unlikely(disk->flags & GENHD_FL_HIDDEN)) {
 		put_disk(disk);
 		disk = NULL;
 	}
-- 
2.14.1