linux-kernel - [PATCH] UBI: fix use after free in ubi_remove

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Date:   Sat, 30 Nov 2019 17:33:17 +0800
From:   Wen Yang <wenyang@...ux.alibaba.com>
To:     Richard Weinberger <richard@....at>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Vignesh Raghavendra <vigneshr@...com>
Cc:     xlpang@...ux.alibaba.com, Wen Yang <wenyang@...ux.alibaba.com>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] UBI: fix use after free in ubi_remove_volume()

We can't use "vol" after it has been freed.

Fixes: 493cfaeaa0c9 ("mtd: utilize new cdev_device_add helper function")
Signed-off-by: Wen Yang <wenyang@...ux.alibaba.com>
Cc: Richard Weinberger <richard@....at>
Cc: Miquel Raynal <miquel.raynal@...tlin.com>
Cc: Vignesh Raghavendra <vigneshr@...com>
Cc: linux-mtd@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org
---
 drivers/mtd/ubi/vmt.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/ubi/vmt.c b/drivers/mtd/ubi/vmt.c
index 139ee13..8ff1478 100644
--- a/drivers/mtd/ubi/vmt.c
+++ b/drivers/mtd/ubi/vmt.c
@@ -375,7 +375,6 @@ int ubi_remove_volume(struct ubi_volume_desc *desc, int no_vtbl)
 	}
 
 	cdev_device_del(&vol->cdev, &vol->dev);
-	put_device(&vol->dev);
 
 	spin_lock(&ubi->volumes_lock);
 	ubi->rsvd_pebs -= reserved_pebs;
@@ -388,6 +387,8 @@ int ubi_remove_volume(struct ubi_volume_desc *desc, int no_vtbl)
 	if (!no_vtbl)
 		self_check_volumes(ubi);
 
+	put_device(&vol->dev);
+
 	return 0;
 
 out_err:
-- 
1.8.3.1