[PATCH -next] Revert "evm: Fix memleak in init_desc"

[xiujianfeng]

Hi, ping....

在 2022/5/27 19:17, Xiu Jianfeng 写道:
> This reverts commit ccf11dbaa07b328fa469415c362d33459c140a37.
>
> Commit ccf11dbaa07b ("evm: Fix memleak in init_desc") said there is
> memleak in init_desc. That may be incorrect, as we can see, tmp_tfm is
> saved in one of the two global variables hmac_tfm or evm_tfm[hash_algo],
> then if init_desc is called next time, there is no need to alloc tfm
> again, so in the error path of kmalloc desc or crypto_shash_init(desc),
> It is not a problem without freeing tmp_tfm.
>
> And also that commit did not reset the global variable to NULL after
> freeing tmp_tfm and this makes *tfm a dangling pointer which may cause a
> UAF issue.
>
> Signed-off-by: Xiu Jianfeng <xiujianfeng at huawei.com>
> ---
>   security/integrity/evm/evm_crypto.c | 7 ++-----
>   1 file changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
> index a733aff02006..708de9656bbd 100644
> --- a/security/integrity/evm/evm_crypto.c
> +++ b/security/integrity/evm/evm_crypto.c
> @@ -75,7 +75,7 @@ static struct shash_desc *init_desc(char type, uint8_t hash_algo)
>   {
>   	long rc;
>   	const char *algo;
> -	struct crypto_shash **tfm, *tmp_tfm = NULL;
> +	struct crypto_shash **tfm, *tmp_tfm;
>   	struct shash_desc *desc;
>   
>   	if (type == EVM_XATTR_HMAC) {
> @@ -120,16 +120,13 @@ static struct shash_desc *init_desc(char type, uint8_t hash_algo)
>   alloc:
>   	desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(*tfm),
>   			GFP_KERNEL);
> -	if (!desc) {
> -		crypto_free_shash(tmp_tfm);
> +	if (!desc)
>   		return ERR_PTR(-ENOMEM);
> -	}
>   
>   	desc->tfm = *tfm;
>   
>   	rc = crypto_shash_init(desc);
>   	if (rc) {
> -		crypto_free_shash(tmp_tfm);
>   		kfree(desc);
>   		return ERR_PTR(rc);
>   	}