Commit 4c7a2e76 authored Apr 27, 2020 by Roberto Sassu Committed by Greg Kroah-Hartman May 27, 2020

evm: Check also if *tfm is an error pointer in init_desc()



[ Upstream commit 53de3b080d5eae31d0de219617155dcc34e7d698 ]

This patch avoids a kernel panic due to accessing an error pointer set by
crypto_alloc_shash(). It occurs especially when there are many files that
require an unsupported algorithm, as it would increase the likelihood of
the following race condition:

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: d46eb369 ("evm: crypto hash replaced by shash")
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>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent 904de138

security/integrity/evm/evm_crypto.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -96,7 +96,7 @@ 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;