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

[Greg Kroah-Hartman]

On Fri, Mar 29, 2019 at 09:28:26PM -0400, Sasha Levin wrote:
> From: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> 
> [ 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@xxxxxxxxxx>
> Reported-and-tested-by: syzbot+b382ba6a802a3d242790@xxxxxxxxxxxxxxxxxxxxxxxxx
> Reported-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
> ---
>  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