Re: [PATCH AUTOSEL 4.19 33/57] blk-mq: protect debugfs_create_files() from failures

Greg Kroah-Hartman
2019-03-30T05:43:16Z

On Fri, Mar 29, 2019 at 09:28:26PM -0400, Sasha Levin wrote:
> From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>
> [ Upstream commit 36991ca68db9dd43bac7f3519f080ee3939263ef ]
>
> If debugfs were to return a non-NULL error for a debugfs call, using
> that pointer later in debugfs_create_files() would crash.
>
> Fix that by properly checking the pointer before referencing it.
>
> Reported-by: Michal Hocko <mhocko@kernel.org>
> Reported-and-tested-by: syzbot+b382ba6a802a3d242790@syzkaller.appspotmail.com
> Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
> block/blk-mq-debugfs.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
> index cb1e6cf7ac48..9dc3a0896462 100644
> --- a/block/blk-mq-debugfs.c
> +++ b/block/blk-mq-debugfs.c
> @@ -806,6 +806,9 @@ static const struct blk_mq_debugfs_attr blk_mq_debugfs_ctx_attrs[] = {
> static bool debugfs_create_files(struct dentry *parent, void *data,
> const struct blk_mq_debugfs_attr *attr)
> {
> + if (IS_ERR_OR_NULL(parent))
> + return false;
> +
> d_inode(parent)->i_private = data;
>
> for (; attr->name; attr++) {
> --
> 2.19.1
>

This was a 5.0-only thing, no need for it to be backported anywhere.
Please drop it from all of your trees.

thanks,

greg k-h