Re: [PATCH] btrfs-progs: Don't return any fs_info that contain NULL tree_root or fs_root.

[Qu Wenruo <quwenruo@cn.fujitsu.com>]

Please ignore this patch since Wang's patch has already fixed them.

https://patchwork.kernel.org/patch/4254631/

Thanks,
Qu
-------- Original Message --------
Subject: [PATCH] btrfs-progs: Don't return any fs_info that contain NULL 
tree_root or fs_root.
From: Qu Wenruo <quwenruo@cn.fujitsu.com>
To: <linux-btrfs@vger.kernel.org>
Date: 2014年09月30日 10:39
> [BUG]
> btrfsck will segfault if it fails to open the fs tree or tree root.
>
> [REPRODUCER]
> Execute btrfsck on a highly damaged btrfs image.
> fsfuzz can be used to make a junk btrfs image.
>
> [REASON]
> Current open_ctree() in btrfs-progs support OPEN_CTREE_PARTIAL flag to
> allow return fs_info even some of the trees is missing.
>
> However it is too loose and even allows fs_info containing no tree to be
> returned.
>
> And when it happens, fs_info->fs_root is NULL,
> close_ctree(fs_info->fs_root) will cause the access to NULL pointer and
> segfault.
>
> [FIX]
> This patch will add checks for fs_info->tree_root and fs_info->fs_root
> before return fs_info.
>
> Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
> ---
>   disk-io.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/disk-io.c b/disk-io.c
> index 26a532e..21a3083 100644
> --- a/disk-io.c
> +++ b/disk-io.c
> @@ -1134,7 +1134,8 @@ static struct btrfs_fs_info *__open_ctree_fd(int fp, const char *path,
>   	return fs_info;
>   
>   out_failed:
> -	if (flags & OPEN_CTREE_PARTIAL)
> +	if (flags & OPEN_CTREE_PARTIAL &&
> +	    fs_info->tree_root && fs_info->fs_root)
>   		return fs_info;
>   out_chunk:
>   	btrfs_release_all_roots(fs_info);