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>
diff --git a/include/linux/crypto.h b/include/linux/crypto.h
index 6eb0610..e8839d3 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