On 23.05.2018 11:06, Su Yue wrote:
> Commit 5a5003df98d5 ("btrfs: delayed-ref: double free in
> btrfs_add_delayed_tree_ref()") fixed double free problem by creating
> an unnessesary label to jump.
> The elegant way is just to change "ref" to "head_ref" and keep
> btrfs_add_delayed_tree_ref() and btrfs_add_delayed_data_ref() in
> similar structure.
I agree, personally I'm a fan of multiple returns rather than jump
labels, because at this point you know the function terminates and
that's it.
>
> This patch reverts commit 5a5003df98d5 ("btrfs: delayed-ref: double
> free in btrfs_add_delayed_tree_ref()") and frees the right head_ref.
> No functional change.
>
> Signed-off-by: Su Yue <suy.f...@cn.fujitsu.com>
Reviewed-by: Nikolay Borisov <nbori...@suse.com>
> ---
> This patch is based on for-next to avoid conflicts with patches
> already in for-next.
>
> fs/btrfs/delayed-ref.c | 21 ++++++++++-----------
> 1 file changed, 10 insertions(+), 11 deletions(-)
>
> diff --git a/fs/btrfs/delayed-ref.c b/fs/btrfs/delayed-ref.c
> index 03dec673d12a..38f8d5d549ed 100644
> --- a/fs/btrfs/delayed-ref.c
> +++ b/fs/btrfs/delayed-ref.c
> @@ -741,14 +741,20 @@ int btrfs_add_delayed_tree_ref(struct btrfs_fs_info
> *fs_info,
> ref->level = level;
>
> head_ref = kmem_cache_alloc(btrfs_delayed_ref_head_cachep, GFP_NOFS);
> - if (!head_ref)
> - goto free_ref;
> + if (!head_ref) {
> + kmem_cache_free(btrfs_delayed_tree_ref_cachep, ref);
> + return -ENOMEM;
> + }
>
> if (test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags) &&
> is_fstree(ref_root)) {
> record = kmalloc(sizeof(*record), GFP_NOFS);
> - if (!record)
> - goto free_head_ref;
> + if (!record) {
> + kmem_cache_free(btrfs_delayed_tree_ref_cachep, ref);
> + kmem_cache_free(btrfs_delayed_ref_head_cachep,
> + head_ref);
> + return -ENOMEM;
> + }
> }
>
> init_delayed_ref_head(head_ref, record, bytenr, num_bytes,
> @@ -779,13 +785,6 @@ int btrfs_add_delayed_tree_ref(struct btrfs_fs_info
> *fs_info,
> btrfs_qgroup_trace_extent_post(fs_info, record);
>
> return 0;
> -
> -free_head_ref:
> - kmem_cache_free(btrfs_delayed_ref_head_cachep, head_ref);
> -free_ref:
> - kmem_cache_free(btrfs_delayed_tree_ref_cachep, ref);
> -
> - return -ENOMEM;
> }
>
> /*
>
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