From: Matthew Garrett <mjg59@google.com>
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 <mjg59@google.com>
Subject: [PATCH V3 1/2] evm: Don't deadlock if a crypto algorithm is unavailable
Date: Fri, 8 Jun 2018 14:57:42 -0700 [thread overview]
Message-ID: <20180608215743.224253-2-mjg59@google.com> (raw)
In-Reply-To: <20180608215743.224253-1-mjg59@google.com>
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>
---
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 494da5fcc092..bea847dc0919 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);
--
2.18.0.rc1.242.g61856ae69a-goog
next prev parent reply other threads:[~2018-06-08 21:57 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-08 21:57 Support additional signature types in EVM Matthew Garrett
2018-06-08 21:57 ` Matthew Garrett [this message]
2018-06-12 17:43 ` [PATCH V3 1/2] evm: Don't deadlock if a crypto algorithm is unavailable Matthew Garrett
2018-06-13 6:33 ` Herbert Xu
2018-06-13 13:50 ` Mimi Zohar
2018-06-08 21:57 ` [PATCH V3 2/2] evm: Allow non-SHA1 digital signatures Matthew Garrett
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180608215743.224253-2-mjg59@google.com \
--to=mjg59@google.com \
--cc=davem@davemloft.net \
--cc=herbert@gondor.apana.org.au \
--cc=linux-crypto@vger.kernel.org \
--cc=linux-integrity@vger.kernel.org \
--cc=zohar@linux.vnet.ibm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.