block: rescan partitions on invalidated devices on -ENOMEDIA too

BugLink: http://bugs.launchpad.net/bugs/793702

commit 02e352287a40bd456eb78df705bf888bc3161d3f upstream.

__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>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 8892870..b6b09cc 100644 (file)
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1099,6 +1099,7 @@ 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) {
@@ -1114,9 +1115,18 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
                                        mutex_unlock(&bdev->bd_mutex);
                                        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);
@@ -1124,8 +1134,6 @@ 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);
@@ -1152,13 +1160,14 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
                put_disk(disk);
                disk = NULL;
                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;
                }
        }
        bdev->bd_openers++;