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Date: Thu, 11 Jan 2018 12:01:19 -0500
From: Theodore Ts'o <tytso@mit.edu>
To: Kees Cook <keescook@chromium.org>
Cc: linux-kernel@vger.kernel.org, David Windsor <dave@nullcore.net>,
        Andreas Dilger <adilger.kernel@dilger.ca>,
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Subject: Re: [PATCH 13/38] ext4: Define usercopy region in ext4_inode_cache
 slab cache
Message-ID: <20180111170119.GB19241@thunk.org>
Mail-Followup-To: Theodore Ts'o <tytso@mit.edu>,
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        Andreas Dilger <adilger.kernel@dilger.ca>,
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        Linus Torvalds <torvalds@linux-foundation.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andy Lutomirski <luto@kernel.org>,
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        Laura Abbott <labbott@redhat.com>,
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        Christoffer Dall <christoffer.dall@linaro.org>,
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On Wed, Jan 10, 2018 at 06:02:45PM -0800, Kees Cook wrote:
> The ext4 symlink pathnames, stored in struct ext4_inode_info.i_data
> and therefore contained in the ext4_inode_cache slab cache, need
> to be copied to/from userspace.

Symlink operations to/from userspace aren't common or in the hot path,
and when they are in i_data, limited to at most 60 bytes.  Is it worth
it to copy through a bounce buffer so as to disallow any usercopies
into struct ext4_inode_info?

					- Ted