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Btrfs: fix a use-after-free bug in btrfs_dev_replace_finishing

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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 <sbehrens@giantdisaster.de>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
This commit is contained in:
Ilya Dryomov 2013-10-02 20:41:01 +03:00 committed by Josef Bacik
parent 964fb15acf
commit 1357272fc7
2 changed files with 7 additions and 5 deletions
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5
fs/btrfs/dev-replace.c
View File

@ -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

7
fs/btrfs/volumes.c
View File

@ -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);
}