From e2861fa71641c6414831d628a1f4f793b6562580 Mon Sep 17 00:00:00 2001 From: Matthew Garrett Date: Fri, 8 Jun 2018 14:57:42 -0700 Subject: evm: Don't deadlock if a crypto algorithm is unavailable When EVM attempts to appraise a file signed with a crypto algorithm the kernel doesn't have support for, it will cause the kernel to trigger a module load. If the EVM policy includes appraisal of kernel modules this will in turn call back into EVM - since EVM is holding a lock until the crypto initialisation is complete, this triggers a deadlock. Add a CRYPTO_NOLOAD flag and skip module loading if it's set, and add that flag in the EVM case in order to fail gracefully with an error message instead of deadlocking. Signed-off-by: Matthew Garrett Acked-by: Herbert Xu Signed-off-by: Mimi Zohar --- security/integrity/evm/evm_crypto.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'security') diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c index b605243108556..c20e3142b541a 100644 --- a/security/integrity/evm/evm_crypto.c +++ b/security/integrity/evm/evm_crypto.c @@ -97,7 +97,8 @@ static struct shash_desc *init_desc(char type) mutex_lock(&mutex); if (*tfm) goto out; - *tfm = crypto_alloc_shash(algo, 0, CRYPTO_ALG_ASYNC); + *tfm = crypto_alloc_shash(algo, 0, + CRYPTO_ALG_ASYNC | CRYPTO_NOLOAD); if (IS_ERR(*tfm)) { rc = PTR_ERR(*tfm); pr_err("Can not allocate %s (reason: %ld)\n", algo, rc); -- cgit v1.2.3