ubi: Fix possible null-ptr-deref in ubi_free_volume()

It willl cause null-ptr-deref in the following case:

uif_init()
  ubi_add_volume()
    cdev_add() -> if it fails, call kill_volumes()
    device_register()

kill_volumes() -> if ubi_add_volume() fails call this function
  ubi_free_volume()
    cdev_del()
    device_unregister() -> trying to delete a not added device,
			   it causes null-ptr-deref

So in ubi_free_volume(), it delete devices whether they are added
or not, it will causes null-ptr-deref.

Handle the error case whlie calling ubi_add_volume() to fix this
problem. If add volume fails, set the corresponding vol to null,
so it can not be accessed in kill_volumes() and release the
resource in ubi_add_volume() error path.

Fixes: 801c135ce73d ("UBI: Unsorted Block Images")
Suggested-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
index eaf3c0c86b2b74594993186a643bd3846bcb907b..5e90a4423b6992d6db6356980af10110df088d0e 100644 (file)
--- a/drivers/mtd/ubi/build.c
+++ b/drivers/mtd/ubi/build.c
@@ -470,6 +470,7 @@ static int uif_init(struct ubi_device *ubi)
                        err = ubi_add_volume(ubi, ubi->volumes[i]);
                        if (err) {
                                ubi_err(ubi, "cannot add volume %d", i);
+                               ubi->volumes[i] = NULL;
                                goto out_volumes;
                        }
                }

diff --git a/drivers/mtd/ubi/vmt.c b/drivers/mtd/ubi/vmt.c
index 9fbc64b997cef3458038d4a69dbfb05f756808c8..2c867d16f89f7de2942f0db6db9b194bd92ee945 100644 (file)
--- a/drivers/mtd/ubi/vmt.c
+++ b/drivers/mtd/ubi/vmt.c
@@ -582,6 +582,7 @@ int ubi_add_volume(struct ubi_device *ubi, struct ubi_volume *vol)
        if (err) {
                ubi_err(ubi, "cannot add character device for volume %d, error %d",
                        vol_id, err);
+               vol_release(&vol->dev);
                return err;
        }
 
@@ -592,15 +593,14 @@ int ubi_add_volume(struct ubi_device *ubi, struct ubi_volume *vol)
        vol->dev.groups = volume_dev_groups;
        dev_set_name(&vol->dev, "%s_%d", ubi->ubi_name, vol->vol_id);
        err = device_register(&vol->dev);
-       if (err)
-               goto out_cdev;
+       if (err) {
+               cdev_del(&vol->cdev);
+               put_device(&vol->dev);
+               return err;
+       }
 
        self_check_volumes(ubi);
        return err;
-
-out_cdev:
-       cdev_del(&vol->cdev);
-       return err;
 }
 
 /**