apparmor: use SHASH_DESC_ON_STACK

When building the kernel with clang, the compiler fails to build
security/apparmor/crypto.c with the following error:

    security/apparmor/crypto.c:36:8: error: fields must have a constant
    size: 'variable length array in structure' extension will never be
    supported
                    char ctx[crypto_shash_descsize(apparmor_tfm)];
                         ^

Since commit a0a77af1 ("crypto: LLVMLinux: Add macro to remove use
of VLAIS in crypto code"), include/crypto/hash.h defines
SHASH_DESC_ON_STACK to work around this issue. Use it in aa_calc_hash()
and aa_calc_profile_hash().
Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
Signed-off-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>

security/apparmor/crypto.c

@@ -31,10 +31,7 @@ unsigned int aa_hash_size(void)
 
 char *aa_calc_hash(void *data, size_t len)
 {
-	struct {
-		struct shash_desc shash;
-		char ctx[crypto_shash_descsize(apparmor_tfm)];
-	} desc;
+	SHASH_DESC_ON_STACK(desc, apparmor_tfm);
 	char *hash = NULL;
 	int error = -ENOMEM;
 
@@ -45,16 +42,16 @@ char *aa_calc_hash(void *data, size_t len)
 	if (!hash)
 		goto fail;
 
-	desc.shash.tfm = apparmor_tfm;
-	desc.shash.flags = 0;
+	desc->tfm = apparmor_tfm;
+	desc->flags = 0;
 
-	error = crypto_shash_init(&desc.shash);
+	error = crypto_shash_init(desc);
 	if (error)
 		goto fail;
-	error = crypto_shash_update(&desc.shash, (u8 *) data, len);
+	error = crypto_shash_update(desc, (u8 *) data, len);
 	if (error)
 		goto fail;
-	error = crypto_shash_final(&desc.shash, hash);
+	error = crypto_shash_final(desc, hash);
 	if (error)
 		goto fail;
 
@@ -69,10 +66,7 @@ char *aa_calc_hash(void *data, size_t len)
 int aa_calc_profile_hash(struct aa_profile *profile, u32 version, void *start,
 			 size_t len)
 {
-	struct {
-		struct shash_desc shash;
-		char ctx[crypto_shash_descsize(apparmor_tfm)];
-	} desc;
+	SHASH_DESC_ON_STACK(desc, apparmor_tfm);
 	int error = -ENOMEM;
 	__le32 le32_version = cpu_to_le32(version);
 
@@ -86,19 +80,19 @@ int aa_calc_profile_hash(struct aa_profile *profile, u32 version, void *start,
 	if (!profile->hash)
 		goto fail;
 
-	desc.shash.tfm = apparmor_tfm;
-	desc.shash.flags = 0;
+	desc->tfm = apparmor_tfm;
+	desc->flags = 0;
 
-	error = crypto_shash_init(&desc.shash);
+	error = crypto_shash_init(desc);
 	if (error)
 		goto fail;
-	error = crypto_shash_update(&desc.shash, (u8 *) &le32_version, 4);
+	error = crypto_shash_update(desc, (u8 *) &le32_version, 4);
 	if (error)
 		goto fail;
-	error = crypto_shash_update(&desc.shash, (u8 *) start, len);
+	error = crypto_shash_update(desc, (u8 *) start, len);
 	if (error)
 		goto fail;
-	error = crypto_shash_final(&desc.shash, profile->hash);
+	error = crypto_shash_final(desc, profile->hash);
 	if (error)
 		goto fail;