diff options
| author | Matthew Garrett <mjg59@google.com> | 2018-06-08 14:57:42 -0700 |
|---|---|---|
| committer | Mimi Zohar <zohar@linux.vnet.ibm.com> | 2018-07-18 07:27:22 -0400 |
| commit | e2861fa71641c6414831d628a1f4f793b6562580 (patch) | |
| tree | e832d4eac8fb33e2838a76cc9457bd3c2d6a2065 | |
| parent | ac2409a521f7ec5978fd582567398d19f4a2fdbd (diff) | |
| download | linux-e2861fa71641c6414831d628a1f4f793b6562580.tar.bz2 | |
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 <mjg59@google.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
| -rw-r--r-- | crypto/api.c | 2 | ||||
| -rw-r--r-- | include/linux/crypto.h | 5 | ||||
| -rw-r--r-- | security/integrity/evm/evm_crypto.c | 3 |
3 files changed, 8 insertions, 2 deletions
diff --git a/crypto/api.c b/crypto/api.c index 0ee632bba064..7aca9f86c5f3 100644 --- a/crypto/api.c +++ b/crypto/api.c @@ -229,7 +229,7 @@ static struct crypto_alg *crypto_larval_lookup(const char *name, u32 type, mask &= ~(CRYPTO_ALG_LARVAL | CRYPTO_ALG_DEAD); alg = crypto_alg_lookup(name, type, mask); - if (!alg) { + if (!alg && !(mask & CRYPTO_NOLOAD)) { request_module("crypto-%s", name); if (!((type ^ CRYPTO_ALG_NEED_FALLBACK) & mask & diff --git a/include/linux/crypto.h b/include/linux/crypto.h index 6eb06101089f..e8839d3a7559 100644 --- a/include/linux/crypto.h +++ b/include/linux/crypto.h @@ -113,6 +113,11 @@ #define CRYPTO_ALG_OPTIONAL_KEY 0x00004000 /* + * Don't trigger module loading + */ +#define CRYPTO_NOLOAD 0x00008000 + +/* * Transform masks and values (for crt_flags). */ #define CRYPTO_TFM_NEED_KEY 0x00000001 diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c index b60524310855..c20e3142b541 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); |