Re: [PATCH v2] Fix NULL pointer dereference in read_cache_folio

[Matthew Wilcox]

On Mon, Sep 30, 2024 at 11:02:26AM +0200, Gianfranco Trad wrote:
> @@ -2360,6 +2360,8 @@ static int filemap_read_folio(struct file *file, filler_t filler,
>  	/* Start the actual read. The read will unlock the page. */
>  	if (unlikely(workingset))
>  		psi_memstall_enter(&pflags);
> +	if (!filler)
> +		return -EIO;

This is definitely wrong because you enter memstall, but do not exit it.

As Andrew says, the underlying problem is that the filesystem does not
implement ->read_folio.  Which filesystem is this?

>  	error = filler(file, folio);
>  	if (unlikely(workingset))
>  		psi_memstall_leave(&pflags);
> -- 
> 2.43.0
>