We need to hold the whole device bd_mutex to protect against
other thread concurrently deleting out partition before we get
to it, and thus causing a use after free.
Fixes: cddae808aeb7 ("block: pass a hd_struct to delete_partition")
Reported-by: syzbot+6448f3c229bc52b82f69@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
block/partitions/core.c | 27 +++++++++++++--------------
1 file changed, 13 insertions(+), 14 deletions(-)
diff --git a/block/partitions/core.c b/block/partitions/core.c
index e62a98a8eeb750..effaa8fd2ee486 100644
--- a/block/partitions/core.c
+++ b/block/partitions/core.c
@@ -524,19 +524,20 @@ int bdev_add_partition(struct block_device *bdev, int partno,
int bdev_del_partition(struct block_device *bdev, int partno)
{
struct block_device *bdevp;
- struct hd_struct *part;
- int ret = 0;
-
- part = disk_get_part(bdev->bd_disk, partno);
- if (!part)
- return -ENXIO;
+ struct hd_struct *part = NULL;
+ int ret;
- ret = -ENOMEM;
- bdevp = bdget(part_devt(part));
+ bdevp = bdget_disk(bdev->bd_disk, partno);
if (!bdevp)
- goto out_put_part;
+ return -ENOMEM;
mutex_lock(&bdevp->bd_mutex);
+ mutex_lock_nested(&bdev->bd_mutex, 1);
+
+ ret = -ENXIO;
+ part = disk_get_part(bdev->bd_disk, partno);
+ if (!part)
+ goto out_unlock;
ret = -EBUSY;
if (bdevp->bd_openers)
@@ -545,16 +546,14 @@ int bdev_del_partition(struct block_device *bdev, int partno)
sync_blockdev(bdevp);
invalidate_bdev(bdevp);
- mutex_lock_nested(&bdev->bd_mutex, 1);
delete_partition(bdev->bd_disk, part);
- mutex_unlock(&bdev->bd_mutex);
-
ret = 0;
out_unlock:
+ mutex_unlock(&bdev->bd_mutex);
mutex_unlock(&bdevp->bd_mutex);
bdput(bdevp);
-out_put_part:
- disk_put_part(part);
+ if (part)
+ disk_put_part(part);
return ret;
}
--
2.28.0
