Re: [PATCH] crypto/block-luks: always set splitkeylen to 0

[Daniel P . Berrangé]

On Wed, Sep 07, 2022 at 09:21:25AM -0700, Patrick Venture wrote:
> This was caught by a sanitized build, that was perhaps oversensitive.
> 
> Signed-off-by: Patrick Venture <venture@google.com>
> ---
>  crypto/block-luks.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/crypto/block-luks.c b/crypto/block-luks.c
> index f62be6836b..8633fb7e9f 100644
> --- a/crypto/block-luks.c
> +++ b/crypto/block-luks.c
> @@ -729,7 +729,7 @@ qcrypto_block_luks_store_key(QCryptoBlock *block,
>      QCryptoBlockLUKS *luks = block->opaque;
>      QCryptoBlockLUKSKeySlot *slot;
>      g_autofree uint8_t *splitkey = NULL;
> -    size_t splitkeylen;
> +    size_t splitkeylen = 0;
>      g_autofree uint8_t *slotkey = NULL;
>      g_autoptr(QCryptoCipher) cipher = NULL;
>      g_autoptr(QCryptoIVGen) ivgen = NULL;
> @@ -901,7 +901,7 @@ qcrypto_block_luks_load_key(QCryptoBlock *block,
>      QCryptoBlockLUKS *luks = block->opaque;
>      const QCryptoBlockLUKSKeySlot *slot;
>      g_autofree uint8_t *splitkey = NULL;
> -    size_t splitkeylen;
> +    size_t splitkeylen = 0;
>      g_autofree uint8_t *possiblekey = NULL;
>      int rv;
>      g_autoptr(QCryptoCipher) cipher = NULL;
> @@ -1147,7 +1147,7 @@ qcrypto_block_luks_erase_key(QCryptoBlock *block,
>      QCryptoBlockLUKS *luks = block->opaque;
>      QCryptoBlockLUKSKeySlot *slot;
>      g_autofree uint8_t *garbagesplitkey = NULL;
> -    size_t splitkeylen;
> +    size_t splitkeylen = 0;
>      size_t i;
>      Error *local_err = NULL;
>      int ret;

In all three cases, splitkeylen is initialized a few lines later.

In qcrypto_block_luks_store_key there is a 'goto cleanup' before
the initialization. The 'cleanup' code can use 'splitkeylen', but
only if 'splitkey != NULL' & this isn't possible if splitkeylen is
uninitialized.

The other two methods have no code path where splitkeylen can be
used uninitialized.

The tool is reporting non-existant problems AFAICT

With regards,
Daniel
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