From: Eric Biggers <ebiggers@kernel.org>
To: linux-fscrypt@vger.kernel.org
Cc: linux-ext4@vger.kernel.org, linux-mtd@lists.infradead.org,
stable@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net
Subject: Re: [PATCH] fscrypt: don't ignore minor_hash when hash is 0
Date: Sat, 5 Jun 2021 00:28:15 -0700 [thread overview]
Message-ID: <YLsnjxXpe+agF6nj@sol.localdomain> (raw)
In-Reply-To: <20210527235236.2376556-1-ebiggers@kernel.org>
On Thu, May 27, 2021 at 04:52:36PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
>
> When initializing a no-key name, fscrypt_fname_disk_to_usr() sets the
> minor_hash to 0 if the (major) hash is 0.
>
> This doesn't make sense because 0 is a valid hash code, so we shouldn't
> ignore the filesystem-provided minor_hash in that case. Fix this by
> removing the special case for 'hash == 0'.
>
> This is an old bug that appears to have originated when the encryption
> code in ext4 and f2fs was moved into fs/crypto/. The original ext4 and
> f2fs code passed the hash by pointer instead of by value. So
> 'if (hash)' actually made sense then, as it was checking whether a
> pointer was NULL. But now the hashes are passed by value, and
> filesystems just pass 0 for any hashes they don't have. There is no
> need to handle this any differently from the hashes actually being 0.
>
> It is difficult to reproduce this bug, as it only made a difference in
> the case where a filename's 32-bit major hash happened to be 0.
> However, it probably had the largest chance of causing problems on
> ubifs, since ubifs uses minor_hash to do lookups of no-key names, in
> addition to using it as a readdir cookie. ext4 only uses minor_hash as
> a readdir cookie, and f2fs doesn't use minor_hash at all.
>
> Fixes: 0b81d0779072 ("fs crypto: move per-file encryption from f2fs tree to fs/crypto")
> Cc: <stable@vger.kernel.org> # v4.6+
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
> fs/crypto/fname.c | 10 +++-------
> 1 file changed, 3 insertions(+), 7 deletions(-)
>
Applied to fscrypt.git#master for 5.14.
- Eric
prev parent reply other threads:[~2021-06-05 7:28 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-27 23:52 [PATCH] fscrypt: don't ignore minor_hash when hash is 0 Eric Biggers
2021-06-05 7:28 ` Eric Biggers [this message]
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