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Date:   Mon, 23 Nov 2020 18:08:31 +0100
From:   David Sterba <dsterba@suse.cz>
To:     Omar Sandoval <osandov@osandov.com>
Cc:     linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org,
        Al Viro <viro@zeniv.linux.org.uk>,
        Christoph Hellwig <hch@infradead.org>,
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        Amir Goldstein <amir73il@gmail.com>,
        Aleksa Sarai <cyphar@cyphar.com>, linux-api@vger.kernel.org,
        kernel-team@fb.com
Subject: Re: [PATCH v6 04/11] btrfs: fix btrfs_write_check()
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References: <cover.1605723568.git.osandov@fb.com>
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On Wed, Nov 18, 2020 at 11:18:11AM -0800, Omar Sandoval wrote:
> From: Omar Sandoval <osandov@fb.com>
> 
> btrfs_write_check() has two related bugs:
> 
> 1. It gets the iov_iter count before calling generic_write_checks(), but
>    generic_write_checks() may truncate the iov_iter.
> 2. It returns the count or negative errno as a size_t, which the callers
>    cast to an int. If the count is greater than INT_MAX, this overflows.
> 
> To fix both of these, pull the call to generic_write_checks() out of
> btrfs_write_check(), use the new iov_iter count returned from
> generic_write_checks(), and have btrfs_write_check() return 0 or a
> negative errno as an int instead of the count. This rearrangement also
> paves the way for RWF_ENCODED write support.
> 
> Fixes: f945968ff64c ("btrfs: introduce btrfs_write_check()")

This patch is still in misc-next and the commit id is unstable, so this
would rather be folded to the patch.