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SubjectRe: [PATCH] evm: Fix memleak in init_desc
On Sat, Jan 09, 2021 at 07:33:05PM +0800, Dinghao Liu wrote:
> When kmalloc() fails, tmp_tfm allocated by
> crypto_alloc_shash() has not been freed, which
> leads to memleak.
>
> Fixes: d46eb3699502b ("evm: crypto hash replaced by shash")
> Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>
> ---
> security/integrity/evm/evm_crypto.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
> index 168c3b78ac47..39fb31a638ac 100644
> --- a/security/integrity/evm/evm_crypto.c
> +++ b/security/integrity/evm/evm_crypto.c
> @@ -73,7 +73,7 @@ static struct shash_desc *init_desc(char type, uint8_t hash_algo)
> {
> long rc;
> const char *algo;
> - struct crypto_shash **tfm, *tmp_tfm;
> + struct crypto_shash **tfm, *tmp_tfm = NULL;
> struct shash_desc *desc;
>
> if (type == EVM_XATTR_HMAC) {
> @@ -118,13 +118,18 @@ 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)
> + if (!desc) {
> + if (tmp_tfm)
> + crypto_free_shash(tmp_tfm);
> return ERR_PTR(-ENOMEM);
> + }
>
> desc->tfm = *tfm;
>
> rc = crypto_shash_init(desc);
> if (rc) {
> + if (tmp_tfm)
> + crypto_free_shash(tmp_tfm);
> kfree(desc);
> return ERR_PTR(rc);
> }

There's no need to check for NULL before calling crypto_free_shash().

- Eric

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