From 1357272fc7deeebb7b3c5d1a071562edc273cdaf Mon Sep 17 00:00:00 2001 From: Ilya Dryomov Date: Wed, 2 Oct 2013 20:41:01 +0300 Subject: Btrfs: fix a use-after-free bug in btrfs_dev_replace_finishing free_device rcu callback, scheduled from btrfs_rm_dev_replace_srcdev, can be processed before btrfs_scratch_superblock is called, which would result in a use-after-free on btrfs_device contents. Fix this by zeroing the superblock before the rcu callback is registered. Cc: Stefan Behrens Signed-off-by: Ilya Dryomov Signed-off-by: Josef Bacik --- fs/btrfs/dev-replace.c | 5 +---- fs/btrfs/volumes.c | 7 ++++++- 2 files changed, 7 insertions(+), 5 deletions(-) diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c index 5d844438b2d4..2a9bd5bd24c3 100644 --- a/fs/btrfs/dev-replace.c +++ b/fs/btrfs/dev-replace.c @@ -535,10 +535,7 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info, list_add(&tgt_device->dev_alloc_list, &fs_info->fs_devices->alloc_list); btrfs_rm_dev_replace_srcdev(fs_info, src_device); - if (src_device->bdev) { - /* zero out the old super */ - btrfs_scratch_superblock(src_device); - } + /* * this is again a consistent state where no dev_replace procedure * is running, the target device is part of the filesystem, the diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 043114749516..b0203b1322ac 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -1716,6 +1716,7 @@ void btrfs_rm_dev_replace_srcdev(struct btrfs_fs_info *fs_info, struct btrfs_device *srcdev) { WARN_ON(!mutex_is_locked(&fs_info->fs_devices->device_list_mutex)); + list_del_rcu(&srcdev->dev_list); list_del_rcu(&srcdev->dev_alloc_list); fs_info->fs_devices->num_devices--; @@ -1725,9 +1726,13 @@ void btrfs_rm_dev_replace_srcdev(struct btrfs_fs_info *fs_info, } if (srcdev->can_discard) fs_info->fs_devices->num_can_discard--; - if (srcdev->bdev) + if (srcdev->bdev) { fs_info->fs_devices->open_devices--; + /* zero out the old super */ + btrfs_scratch_superblock(srcdev); + } + call_rcu(&srcdev->rcu, free_device); } -- cgit v1.2.2