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From: Herbert Xu <herbert@gondor.apana.org.au>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: linux-crypto@vger.kernel.org,
	Sami Tolvanen <samitolvanen@google.com>,
	Eric Biggers <ebiggers@kernel.org>
Subject: Re: [PATCH v3] crypto: shash - avoid comparing pointers to exported functions under CFI
Date: Thu, 17 Jun 2021 16:01:03 +0800	[thread overview]
Message-ID: <20210617080103.GC10662@gondor.apana.org.au> (raw)
In-Reply-To: <20210610062150.212779-1-ardb@kernel.org>

On Thu, Jun 10, 2021 at 08:21:50AM +0200, Ard Biesheuvel wrote:
> crypto_shash_alg_has_setkey() is implemented by testing whether the
> .setkey() member of a struct shash_alg points to the default version,
> called shash_no_setkey(). As crypto_shash_alg_has_setkey() is a static
> inline, this requires shash_no_setkey() to be exported to modules.
> 
> Unfortunately, when building with CFI, function pointers are routed
> via CFI stubs which are private to each module (or to the kernel proper)
> and so this function pointer comparison may fail spuriously.
> 
> Let's fix this by turning crypto_shash_alg_has_setkey() into an out of
> line function.
> 
> Cc: Sami Tolvanen <samitolvanen@google.com>
> Cc: Eric Biggers <ebiggers@kernel.org>
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
> v3: improve comment as per Eric's suggestion
> v2: add code comment to explain why the function needs to remain out of
> line
> 
>  crypto/shash.c                 | 18 +++++++++++++++---
>  include/crypto/internal/hash.h |  8 +-------
>  2 files changed, 16 insertions(+), 10 deletions(-)

Patch applied.  Thanks.
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

      parent reply	other threads:[~2021-06-17  8:01 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-10  6:21 [PATCH v3] crypto: shash - avoid comparing pointers to exported functions under CFI Ard Biesheuvel
2021-06-10 18:48 ` Eric Biggers
2021-06-10 20:39   ` Sami Tolvanen
2021-06-17  8:01 ` Herbert Xu [this message]

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