From: Nikolay Borisov <nborisov@suse.com>
To: Josef Bacik <josef@toxicpanda.com>,
linux-btrfs@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH 2/8] btrfs: do not init a reloc root if we aren't relocating
Date: Wed, 4 Mar 2020 20:44:04 +0200 [thread overview]
Message-ID: <27cd0745-6e4c-be69-5604-00b36a3cfcd7@suse.com> (raw)
In-Reply-To: <20200304161830.2360-3-josef@toxicpanda.com>
On 4.03.20 г. 18:18 ч., Josef Bacik wrote:
> We previously were checking if the root had a dead root before accessing
> root->reloc_root in order to avoid a UAF type bug. However this
> scenario happens after we've unset the reloc control, so we would have
> been saved if we'd simply checked for fs_info->reloc_control. At this
> point during relocation we no longer need to be creating new reloc
> roots, so simply move this check above the reloc_root checks to avoid
> any future races and confusion.
>
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Doesn't this patch essentially obviate the reloc_root_is_dead. W.r.t
->reloc_ctl it's important to note that it's being set under reloc_mutex
which this function is also called under so we are guaranteed consistent
value.
> ---
> fs/btrfs/relocation.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
> index 507361e99316..2141519a9dd0 100644
> --- a/fs/btrfs/relocation.c
> +++ b/fs/btrfs/relocation.c
> @@ -1527,6 +1527,10 @@ int btrfs_init_reloc_root(struct btrfs_trans_handle *trans,
> int clear_rsv = 0;
> int ret;
>
> + if (!rc || !rc->create_reloc_tree ||
> + root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
> + return 0;
> +
> /*
> * The subvolume has reloc tree but the swap is finished, no need to
> * create/update the dead reloc tree
> @@ -1540,10 +1544,6 @@ int btrfs_init_reloc_root(struct btrfs_trans_handle *trans,
> return 0;
> }
>
> - if (!rc || !rc->create_reloc_tree ||
> - root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
> - return 0;
> -
> if (!trans->reloc_reserved) {
> rsv = trans->block_rsv;
> trans->block_rsv = rc->block_rsv;
>
next prev parent reply other threads:[~2020-03-04 18:44 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-04 16:18 [PATCH 0/8][v2] relocation error handling fixes Josef Bacik
2020-03-04 16:18 ` [PATCH 1/8] btrfs: drop block from cache on error in relocation Josef Bacik
2020-03-05 11:37 ` Qu Wenruo
2020-03-04 16:18 ` [PATCH 2/8] btrfs: do not init a reloc root if we aren't relocating Josef Bacik
2020-03-04 18:44 ` Nikolay Borisov [this message]
2020-03-04 18:47 ` Josef Bacik
2020-03-05 11:24 ` Qu Wenruo
2020-03-04 16:18 ` [PATCH 3/8] btrfs: unset reloc control if we fail to recover Josef Bacik
2020-03-05 11:38 ` Qu Wenruo
2020-03-04 16:18 ` [PATCH 4/8] btrfs: free the reloc_control in a consistent way Josef Bacik
2020-03-05 11:39 ` Qu Wenruo
2020-03-13 15:18 ` David Sterba
2020-03-13 15:32 ` Josef Bacik
2020-03-14 0:13 ` Qu Wenruo
2020-03-04 16:18 ` [PATCH 5/8] btrfs: run clean_dirty_subvols if we fail to start a trans Josef Bacik
2020-03-05 11:40 ` Qu Wenruo
2020-03-05 17:46 ` David Sterba
2020-03-04 16:18 ` [PATCH 6/8] btrfs: clear BTRFS_ROOT_DEAD_RELOC_TREE before dropping the reloc root Josef Bacik
2020-03-05 11:41 ` Qu Wenruo
2020-03-05 13:54 ` Josef Bacik
2020-03-04 16:18 ` [PATCH 7/8] btrfs: hold a ref on the root->reloc_root Josef Bacik
2020-03-04 16:18 ` [PATCH 8/8] btrfs: remove a BUG_ON() from merge_reloc_roots() Josef Bacik
2020-03-13 14:35 ` [PATCH 0/8][v2] relocation error handling fixes David Sterba
2020-03-13 15:44 [PATCH 0/8][v3] " Josef Bacik
2020-03-13 15:44 ` [PATCH 2/8] btrfs: do not init a reloc root if we aren't relocating Josef Bacik
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