fscrypt: improve warnings for missing crypto API support

Users of fscrypt with non-default algorithms will encounter an error
like the following if they fail to include the needed algorithms into
the crypto API when configuring the kernel (as per the documentation):

    Error allocating 'adiantum(xchacha12,aes)' transform: -2

This requires that the user figure out what the "-2" error means.
Make it more friendly by printing a warning like the following instead:

    Missing crypto API support for Adiantum (API name: "adiantum(xchacha12,aes)")

Also upgrade the log level for *other* errors to KERN_ERR.

Signed-off-by: Eric Biggers <ebiggers@google.com>

diff --git a/fs/crypto/keyinfo.c b/fs/crypto/keyinfo.c
index e5ab18d..b756785 100644 (file)
--- a/fs/crypto/keyinfo.c
+++ b/fs/crypto/keyinfo.c
@@ -237,8 +237,13 @@ allocate_skcipher_for_mode(struct fscrypt_mode *mode, const u8 *raw_key,
 
        tfm = crypto_alloc_skcipher(mode->cipher_str, 0, 0);
        if (IS_ERR(tfm)) {
-               fscrypt_warn(inode, "Error allocating '%s' transform: %ld",
-                            mode->cipher_str, PTR_ERR(tfm));
+               if (PTR_ERR(tfm) == -ENOENT)
+                       fscrypt_warn(inode,
+                                    "Missing crypto API support for %s (API name: \"%s\")",
+                                    mode->friendly_name, mode->cipher_str);
+               else
+                       fscrypt_err(inode, "Error allocating '%s' transform: %ld",
+                                   mode->cipher_str, PTR_ERR(tfm));
                return tfm;
        }
        if (unlikely(!mode->logged_impl_name)) {
@@ -384,9 +389,13 @@ static int derive_essiv_salt(const u8 *key, int keysize, u8 *salt)
 
                tfm = crypto_alloc_shash("sha256", 0, 0);
                if (IS_ERR(tfm)) {
-                       fscrypt_warn(NULL,
-                                    "error allocating SHA-256 transform: %ld",
-                                    PTR_ERR(tfm));
+                       if (PTR_ERR(tfm) == -ENOENT)
+                               fscrypt_warn(NULL,
+                                            "Missing crypto API support for SHA-256");
+                       else
+                               fscrypt_err(NULL,
+                                           "Error allocating SHA-256 transform: %ld",
+                                           PTR_ERR(tfm));
                        return PTR_ERR(tfm);
                }
                prev_tfm = cmpxchg(&essiv_hash_tfm, NULL, tfm);