block: rescan partitions on invalidated devices on -ENOMEDIA too

__blkdev_get() doesn't rescan partitions if disk->fops->open() fails,
which leads to ghost partition devices lingering after medimum removal
is known to both the kernel and userland.  The behavior also creates a
subtle inconsistency where O_NONBLOCK open, which doesn't fail even if
there's no medium, clears the ghots partitions, which is exploited to
work around the problem from userland.

Fix it by updating __blkdev_get() to issue partition rescan after
-ENOMEDIA too.

This was reported in the following bz.

 https://bugzilla.kernel.org/show_bug.cgi?id=13029

Stable: 2.6.38

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: David Zeuthen <zeuthen@gmail.com>
Reported-by: Martin Pitt <martin.pitt@ubuntu.com>
Reported-by: Kay Sievers <kay.sievers@vrfy.org>
Tested-by: Kay Sievers <kay.sievers@vrfy.org>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: stable@kernel.org
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

1 files changed, 18 insertions, 9 deletions

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 5147bdd3b8e..257b00e9842 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1102,6 +1102,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
                         if (!bdev->bd_part)
                                 goto out_clear;
 
+                        ret = 0;
                         if (disk->fops->open) {
                                 ret = disk->fops->open(bdev, mode);
                                 if (ret == -ERESTARTSYS) {
@@ -1118,9 +1119,18 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
                                         put_disk(disk);
                                         goto restart;
                                 }
-                                if (ret)
-                                        goto out_clear;
                         }
+                        /*
+                         * If the device is invalidated, rescan partition
+                         * if open succeeded or failed with -ENOMEDIUM.
+                         * The latter is necessary to prevent ghost
+                         * partitions on a removed medium.
+                         */
+                        if (bdev->bd_invalidated && (!ret || ret == -ENOMEDIUM))
+                                rescan_partitions(disk, bdev);
+                        if (ret)
+                                goto out_clear;
+
                         if (!bdev->bd_openers) {
                                 bd_set_size(bdev,(loff_t)get_capacity(disk)<<9);
                                 bdi = blk_get_backing_dev_info(bdev);
@@ -1128,8 +1138,6 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
                                         bdi = &default_backing_dev_info;
                                 bdev_inode_switch_bdi(bdev->bd_inode, bdi);
                         }
-                        if (bdev->bd_invalidated)
-                                rescan_partitions(disk, bdev);
                 } else {
                         struct block_device *whole;
                         whole = bdget_disk(disk, 0);
@@ -1153,13 +1161,14 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
                 }
         } else {
                 if (bdev->bd_contains == bdev) {
-                        if (bdev->bd_disk->fops->open) {
+                        ret = 0;
+                        if (bdev->bd_disk->fops->open)
                                 ret = bdev->bd_disk->fops->open(bdev, mode);
-                                if (ret)
-                                        goto out_unlock_bdev;
-                        }
-                        if (bdev->bd_invalidated)
+                        /* the same as first opener case, read comment there */
+                        if (bdev->bd_invalidated && (!ret || ret == -ENOMEDIUM))
                                 rescan_partitions(bdev->bd_disk, bdev);
+                        if (ret)
+                                goto out_unlock_bdev;
                 }
                 /* only one opener holds refs to the module and disk */
                 module_put(disk->fops->owner);