From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f202.google.com ([209.85.223.202]:52395 "EHLO mail-io0-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750842AbeFAXCz (ORCPT ); Fri, 1 Jun 2018 19:02:55 -0400 Received: by mail-io0-f202.google.com with SMTP id k21-v6so21866568ioj.19 for ; Fri, 01 Jun 2018 16:02:55 -0700 (PDT) MIME-Version: 1.0 Date: Fri, 1 Jun 2018 16:02:43 -0700 Message-Id: <20180601230244.138560-1-mjg59@google.com> Subject: [PATCH 1/2] evm: Don't deadlock if a crypto algorithm is unavailable From: Matthew Garrett To: linux-integrity@vger.kernel.org Cc: zohar@linux.vnet.ibm.com, linux-crypto@vger.kernel.org, herbert@gondor.apana.org.au, davem@davemloft.net, Matthew Garrett Content-Type: text/plain; charset="UTF-8" Sender: linux-integrity-owner@vger.kernel.org List-ID: Trying to instantiate a non-existent crypto algorithm will cause the kernel to trigger a module load. If EVM appraisal is enabled, this will in turn trigger appraisal of the module, which will fail because the crypto algorithm isn't available. Add a CRYPTO_NOLOAD flag and skip module loading if it's set, and add that flag in the EVM case. Signed-off-by: Matthew Garrett --- crypto/api.c | 2 +- include/linux/crypto.h | 5 +++++ 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 @@ -112,6 +112,11 @@ */ #define CRYPTO_ALG_OPTIONAL_KEY 0x00004000 +/* + * Don't trigger module loading + */ +#define CRYPTO_NOLOAD 0x00008000 + /* * Transform masks and values (for crt_flags). */ diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c index a46fba322340..ccafc9468611 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); -- 2.17.1.1185.g55be947832-goog