block: Fix NULL pointer dereference in sd_revalidate_disk

Since 2.6.39 (1196f8b), when a driver returns -ENOMEDIUM for open(),
__blkdev_get() calls rescan_partitions() to remove
in-kernel partition structures and raise KOBJ_CHANGE uevent.

However it ends up calling driver's revalidate_disk without open
and could cause oops.

In the case of SCSI:

  process A                  process B
  ----------------------------------------------
  sys_open
    __blkdev_get
      sd_open
        returns -ENOMEDIUM
                             scsi_remove_device
                               <scsi_device torn down>
      rescan_partitions
        sd_revalidate_disk
          <oops>
Oopses are reported here:
http://marc.info/?l=linux-scsi&m=132388619710052

This patch separates the partition invalidation from rescan_partitions()
and use it for -ENOMEDIUM case.

Reported-by: Huajun Li <huajun.li.lee@gmail.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: stable@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 40 insertions, 8 deletions

diff --git a/block/partition-generic.c b/block/partition-generic.c
index d06ec1c829c2..6df5d6928a44 100644
--- a/block/partition-generic.c
+++ b/block/partition-generic.c
@@ -389,17 +389,11 @@ static bool disk_unlock_native_capacity(struct gendisk *disk)
         }
 }
 
-int rescan_partitions(struct gendisk *disk, struct block_device *bdev)
+static int drop_partitions(struct gendisk *disk, struct block_device *bdev)
 {
-        struct parsed_partitions *state = NULL;
         struct disk_part_iter piter;
         struct hd_struct *part;
-        int p, highest, res;
-rescan:
-        if (state && !IS_ERR(state)) {
-                kfree(state);
-                state = NULL;
-        }
+        int res;
 
         if (bdev->bd_part_count)
                 return -EBUSY;
@@ -412,6 +406,24 @@ rescan:
                 delete_partition(disk, part->partno);
         disk_part_iter_exit(&piter);
 
+        return 0;
+}
+
+int rescan_partitions(struct gendisk *disk, struct block_device *bdev)
+{
+        struct parsed_partitions *state = NULL;
+        struct hd_struct *part;
+        int p, highest, res;
+rescan:
+        if (state && !IS_ERR(state)) {
+                kfree(state);
+                state = NULL;
+        }
+
+        res = drop_partitions(disk, bdev);
+        if (res)
+                return res;
+
         if (disk->fops->revalidate_disk)
                 disk->fops->revalidate_disk(disk);
         check_disk_size_change(disk, bdev);
@@ -515,6 +527,26 @@ rescan:
         return 0;
 }
 
+int invalidate_partitions(struct gendisk *disk, struct block_device *bdev)
+{
+        int res;
+
+        if (!bdev->bd_invalidated)
+                return 0;
+
+        res = drop_partitions(disk, bdev);
+        if (res)
+                return res;
+
+        set_capacity(disk, 0);
+        check_disk_size_change(disk, bdev);
+        bdev->bd_invalidated = 0;
+        /* tell userspace that the media / partition table may have changed */
+        kobject_uevent(&disk_to_dev(disk)->kobj, KOBJ_CHANGE);
+
+        return 0;
+}
+
 unsigned char *read_dev_sector(struct block_device *bdev, sector_t n, Sector *p)
 {
         struct address_space *mapping = bdev->bd_inode->i_mapping;