The mutex in init_desc(), introduced by commit 97426f985729 ("evm: prevent racing during tfm allocation") prevents two tasks to concurrently set *tfm. However, checking if *tfm is NULL is not enough, as crypto_alloc_shash() can return an error pointer. The following sequence can happen:
Task A: *tfm = crypto_alloc_shash() <= error pointer Task B: if (*tfm == NULL) <= *tfm is not NULL, use it Task B: rc = crypto_shash_init(desc) <= panic Task A: *tfm = NULL
This patch uses the IS_ERR_OR_NULL macro to determine whether or not a new crypto context must be created.
Cc: stable@vger.kernel.org Fixes: 97426f985729 ("evm: prevent racing during tfm allocation") Co-developed-by: Krzysztof Struczynski krzysztof.struczynski@huawei.com Signed-off-by: Krzysztof Struczynski krzysztof.struczynski@huawei.com Signed-off-by: Roberto Sassu roberto.sassu@huawei.com --- security/integrity/evm/evm_crypto.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c index 35682852ddea..77ad1e5a93e4 100644 --- a/security/integrity/evm/evm_crypto.c +++ b/security/integrity/evm/evm_crypto.c @@ -91,7 +91,7 @@ static struct shash_desc *init_desc(char type, uint8_t hash_algo) algo = hash_algo_name[hash_algo]; }
- if (*tfm == NULL) { + if (IS_ERR_OR_NULL(*tfm)) { mutex_lock(&mutex); if (*tfm) goto out;