fscrypt: stop pretending that key setup is nofs-safe

fscrypt_get_encryption_info() has never actually been safe to call in a
context that needs GFP_NOFS, since it calls crypto_alloc_skcipher().

crypto_alloc_skcipher() isn't GFP_NOFS-safe, even if called under
memalloc_nofs_save().  This is because it may load kernel modules, and
also because it internally takes crypto_alg_sem.  Other tasks can do
GFP_KERNEL allocations while holding crypto_alg_sem for write.

The use of fscrypt_init_mutex isn't GFP_NOFS-safe either.

So, stop pretending that fscrypt_get_encryption_info() is nofs-safe.
I.e., when it allocates memory, just use GFP_KERNEL instead of GFP_NOFS.

Note, another reason to do this is that GFP_NOFS is deprecated in favor
of using memalloc_nofs_save() in the proper places.

Acked-by: Jeff Layton <jlayton@kernel.org>
Link: https://lore.kernel.org/r/20200917041136.178600-10-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>

fs/crypto/inline_crypt.c

@@ -106,7 +106,7 @@ int fscrypt_select_encryption_impl(struct fscrypt_info *ci)
 	crypto_cfg.data_unit_size = sb->s_blocksize;
 	crypto_cfg.dun_bytes = fscrypt_get_dun_bytes(ci);
 	num_devs = fscrypt_get_num_devices(sb);
-	devs = kmalloc_array(num_devs, sizeof(*devs), GFP_NOFS);
+	devs = kmalloc_array(num_devs, sizeof(*devs), GFP_KERNEL);
 	if (!devs)
 		return -ENOMEM;
 	fscrypt_get_devices(sb, num_devs, devs);
@@ -135,9 +135,8 @@ int fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key,
 	struct fscrypt_blk_crypto_key *blk_key;
 	int err;
 	int i;
-	unsigned int flags;
 
-	blk_key = kzalloc(struct_size(blk_key, devs, num_devs), GFP_NOFS);
+	blk_key = kzalloc(struct_size(blk_key, devs, num_devs), GFP_KERNEL);
 	if (!blk_key)
 		return -ENOMEM;
 
@@ -166,10 +165,8 @@ int fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key,
 		}
 		queue_refs++;
 
-		flags = memalloc_nofs_save();
 		err = blk_crypto_start_using_key(&blk_key->base,
 						 blk_key->devs[i]);
-		memalloc_nofs_restore(flags);
 		if (err) {
 			fscrypt_err(inode,
 				    "error %d starting to use blk-crypto", err);

fs/crypto/keysetup.c

@@ -488,7 +488,7 @@ fscrypt_setup_encryption_info(struct inode *inode,
 	if (res)
 		return res;
 
-	crypt_info = kmem_cache_zalloc(fscrypt_info_cachep, GFP_NOFS);
+	crypt_info = kmem_cache_zalloc(fscrypt_info_cachep, GFP_KERNEL);
 	if (!crypt_info)
 		return -ENOMEM;
 

fs/crypto/keysetup_v1.c

@@ -60,7 +60,7 @@ static int derive_key_aes(const u8 *master_key,
 		goto out;
 	}
 	crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS);
-	req = skcipher_request_alloc(tfm, GFP_NOFS);
+	req = skcipher_request_alloc(tfm, GFP_KERNEL);
 	if (!req) {
 		res = -ENOMEM;
 		goto out;
@@ -99,7 +99,7 @@ find_and_lock_process_key(const char *prefix,
 	const struct user_key_payload *ukp;
 	const struct fscrypt_key *payload;
 
-	description = kasprintf(GFP_NOFS, "%s%*phN", prefix,
+	description = kasprintf(GFP_KERNEL, "%s%*phN", prefix,
 				FSCRYPT_KEY_DESCRIPTOR_SIZE, descriptor);
 	if (!description)
 		return ERR_PTR(-ENOMEM);
@@ -228,7 +228,7 @@ fscrypt_get_direct_key(const struct fscrypt_info *ci, const u8 *raw_key)
 		return dk;
 
 	/* Nope, allocate one. */
-	dk = kzalloc(sizeof(*dk), GFP_NOFS);
+	dk = kzalloc(sizeof(*dk), GFP_KERNEL);
 	if (!dk)
 		return ERR_PTR(-ENOMEM);
 	refcount_set(&dk->dk_refcount, 1);
@@ -272,7 +272,7 @@ static int setup_v1_file_key_derived(struct fscrypt_info *ci,
 	 * This cannot be a stack buffer because it will be passed to the
 	 * scatterlist crypto API during derive_key_aes().
 	 */
-	derived_key = kmalloc(ci->ci_mode->keysize, GFP_NOFS);
+	derived_key = kmalloc(ci->ci_mode->keysize, GFP_KERNEL);
 	if (!derived_key)
 		return -ENOMEM;