linux-kernel - Re: [PATCH 5.4 129/270] iomap: Make sure iomap_end is called after iomap

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Date:   Mon, 17 Aug 2020 21:59:03 +0200
From:   Andreas Gruenbacher <agruenba@...hat.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        stable <stable@...r.kernel.org>, Christoph Hellwig <hch@....de>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 5.4 129/270] iomap: Make sure iomap_end is called after iomap_begin

Greg,

On Mon, Aug 17, 2020 at 6:06 PM Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
> From: Andreas Gruenbacher <agruenba@...hat.com>
>
> [ Upstream commit 856473cd5d17dbbf3055710857c67a4af6d9fcc0 ]
>
> Make sure iomap_end is always called when iomap_begin succeeds.
>
> Without this fix, iomap_end won't be called when a filesystem's
> iomap_begin operation returns an invalid mapping, bypassing any
> unlocking done in iomap_end.  With this fix, the unlocking will still
> happen.
>
> This bug was found by Bob Peterson during code review.  It's unlikely
> that such iomap_begin bugs will survive to affect users, so backporting
> this fix seems unnecessary.

as said for 5.7 / 5.8 already, this patch doesn't need to be backported.

Thanks,
Andreas

> Fixes: ae259a9c8593 ("fs: introduce iomap infrastructure")
> Signed-off-by: Andreas Gruenbacher <agruenba@...hat.com>
> Reviewed-by: Christoph Hellwig <hch@....de>
> Reviewed-by: Darrick J. Wong <darrick.wong@...cle.com>
> Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
> Signed-off-by: Sasha Levin <sashal@...nel.org>
> ---
>  fs/iomap/apply.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/fs/iomap/apply.c b/fs/iomap/apply.c
> index 54c02aecf3cd8..c2281a6a7f320 100644
> --- a/fs/iomap/apply.c
> +++ b/fs/iomap/apply.c
> @@ -41,10 +41,14 @@ iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags,
>         ret = ops->iomap_begin(inode, pos, length, flags, &iomap);
>         if (ret)
>                 return ret;
> -       if (WARN_ON(iomap.offset > pos))
> -               return -EIO;
> -       if (WARN_ON(iomap.length == 0))
> -               return -EIO;
> +       if (WARN_ON(iomap.offset > pos)) {
> +               written = -EIO;
> +               goto out;
> +       }
> +       if (WARN_ON(iomap.length == 0)) {
> +               written = -EIO;
> +               goto out;
> +       }
>
>         /*
>          * Cut down the length to the one actually provided by the filesystem,
> @@ -60,6 +64,7 @@ iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags,
>          */
>         written = actor(inode, pos, length, data, &iomap);
>
> +out:
>         /*
>          * Now the data has been copied, commit the range we've copied.  This
>          * should not fail unless the filesystem has had a fatal error.
> --
> 2.25.1
>
>
>