MODSIGN: Don't use enum-type bitfields in module signature info block

Don't use enum-type bitfields in the module signature info block as we can't be
certain how the compiler will handle them.  As I understand it, it is arch
dependent, and it is possible for the compiler to rearrange them based on
endianness and to insert a byte of padding to pad the three enums out to four
bytes.

Instead use u8 fields for these, which the compiler should emit in the right
order without padding.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

diff --git a/kernel/module_signing.c b/kernel/module_signing.c
index ea1b1df..f2970bd 100644 (file)
--- a/kernel/module_signing.c
+++ b/kernel/module_signing.c
@@ -27,13 +27,13 @@
  *     - Information block
  */
 struct module_signature {
-       enum pkey_algo          algo : 8;       /* Public-key crypto algorithm */
-       enum pkey_hash_algo     hash : 8;       /* Digest algorithm */
-       enum pkey_id_type       id_type : 8;    /* Key identifier type */
-       u8                      signer_len;     /* Length of signer's name */
-       u8                      key_id_len;     /* Length of key identifier */
-       u8                      __pad[3];
-       __be32                  sig_len;        /* Length of signature data */
+       u8      algo;           /* Public-key crypto algorithm [enum pkey_algo] */
+       u8      hash;           /* Digest algorithm [enum pkey_hash_algo] */
+       u8      id_type;        /* Key identifier type [enum pkey_id_type] */
+       u8      signer_len;     /* Length of signer's name */
+       u8      key_id_len;     /* Length of key identifier */
+       u8      __pad[3];
+       __be32  sig_len;        /* Length of signature data */
 };
 
 /*