linux-kernel - [PATCH v2] Fix NULL pointer dereference in bl_free

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Date:	Tue, 19 Jul 2016 17:39:04 +0200
From:	Artem Savkov <asavkov@...hat.com>
To:	Anna Schumaker <Anna.Schumaker@...app.com>
Cc:	linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org,
	trond.myklebust@...marydata.com, hch@....de,
	Artem Savkov <asavkov@...hat.com>
Subject: [PATCH v2] Fix NULL pointer dereference in bl_free_device().

When bl_parse_deviceid() fails in bl_alloc_deviceid_node() on
blkdev_get_by_*() step we get an pnfs_block_dev struct that is
uninitialized except for bdev field which is set to whatever error
blkdev_get_by_*() returns.  bl_free_device() then tries to call
blkdev_put() if bdev is not 0 resulting in a wrong pointer dereference.

Fixing this by making sure bdev is not an error code in bl_free_device().

Signed-off-by: Artem Savkov <asavkov@...hat.com>
---
 fs/nfs/blocklayout/dev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/nfs/blocklayout/dev.c b/fs/nfs/blocklayout/dev.c
index 118252f..57cb800 100644
--- a/fs/nfs/blocklayout/dev.c
+++ b/fs/nfs/blocklayout/dev.c
@@ -33,7 +33,7 @@ bl_free_device(struct pnfs_block_dev *dev)
 				pr_err("failed to unregister PR key.\n");
 		}

-		if (dev->bdev)
+		if (!IS_ERR_OR_NULL(dev->bdev))
 			blkdev_put(dev->bdev, FMODE_READ | FMODE_WRITE);
 	}
 }
-- 
2.5.5