linux-kernel - Re: [PATCH] mm: validate inode in mapping_set

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Date:   Sat, 10 Oct 2020 07:58:58 -0400
From:   Jeff Layton <jlayton@...nel.org>
To:     Minchan Kim <minchan@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Jan Kara <jack@...e.cz>, linux-mm <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: validate inode in mapping_set_error

On Fri, 2020-10-09 at 17:06 -0700, Minchan Kim wrote:
> The swap address_space doesn't have host. Thus, it makes kernel crash once
> swap write meets error. Fix it.
> 
> [1] 735e4ae5ba28, vfs: track per-sb writeback errors and report them to syncfs
> Signed-off-by: Minchan Kim <minchan@...nel.org>
> ---
>  include/linux/pagemap.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index 17ba0fe59290..9cf540447e73 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -55,7 +55,8 @@ static inline void mapping_set_error(struct address_space *mapping, int error)
>  	__filemap_set_wb_err(mapping, error);
>  
>  	/* Record it in superblock */
> -	errseq_set(&mapping->host->i_sb->s_wb_err, error);
> +	if (mapping->host)
> +		errseq_set(&mapping->host->i_sb->s_wb_err, error);
>  
>  	/* Record it in flags for now, for legacy callers */
>  	if (error == -ENOSPC)

Good catch.

Acked-by: Jeff Layton <jlayton@...nel.org>