block: Fix NULL pointer dereference in sd_revalidate_disk
Jun'ichi Nomura [Fri, 2 Mar 2012 09:38:33 +0000 (10:38 +0100)]
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>

block/partition-generic.c
fs/block_dev.c
include/linux/genhd.h

index d06ec1c..6df5d69 100644 (file)
@@ -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;
index 0e575d1..5e9f198 100644 (file)
@@ -1183,8 +1183,12 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
                         * The latter is necessary to prevent ghost
                         * partitions on a removed medium.
                         */
-                       if (bdev->bd_invalidated && (!ret || ret == -ENOMEDIUM))
-                               rescan_partitions(disk, bdev);
+                       if (bdev->bd_invalidated) {
+                               if (!ret)
+                                       rescan_partitions(disk, bdev);
+                               else if (ret == -ENOMEDIUM)
+                                       invalidate_partitions(disk, bdev);
+                       }
                        if (ret)
                                goto out_clear;
                } else {
@@ -1214,8 +1218,12 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
                        if (bdev->bd_disk->fops->open)
                                ret = bdev->bd_disk->fops->open(bdev, mode);
                        /* the same as first opener case, read comment there */
-                       if (bdev->bd_invalidated && (!ret || ret == -ENOMEDIUM))
-                               rescan_partitions(bdev->bd_disk, bdev);
+                       if (bdev->bd_invalidated) {
+                               if (!ret)
+                                       rescan_partitions(bdev->bd_disk, bdev);
+                               else if (ret == -ENOMEDIUM)
+                                       invalidate_partitions(bdev->bd_disk, bdev);
+                       }
                        if (ret)
                                goto out_unlock_bdev;
                }
index fe23ee7..e61d319 100644 (file)
@@ -596,6 +596,7 @@ extern char *disk_name (struct gendisk *hd, int partno, char *buf);
 
 extern int disk_expand_part_tbl(struct gendisk *disk, int target);
 extern int rescan_partitions(struct gendisk *disk, struct block_device *bdev);
+extern int invalidate_partitions(struct gendisk *disk, struct block_device *bdev);
 extern struct hd_struct * __must_check add_partition(struct gendisk *disk,
                                                     int partno, sector_t start,
                                                     sector_t len, int flags,