fscrypt: stop holding extra request_queue references

Now that the fscrypt_master_key lifetime has been reworked to not be
subject to the quirks of the keyrings subsystem, blk_crypto_evict_key()
no longer gets called after the filesystem has already been unmounted.
Therefore, there is no longer any need to hold extra references to the
filesystem's request_queue(s). (And these references didn't always do
their intended job anyway, as pinning a request_queue doesn't
necessarily pin the corresponding blk_crypto_profile.)

Stop taking these extra references. Instead, just pass the super_block
to fscrypt_destroy_inline_crypt_key(), and use it to get the list of
block devices the key needs to be evicted from.

Signed-off-by: Eric Biggers <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

fs/crypto/fscrypt_private.h

···
 struct fscrypt_prepared_key {
 	struct crypto_skcipher *tfm;
 #ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
-	struct fscrypt_blk_crypto_key *blk_key;
+	struct blk_crypto_key *blk_key;
 #endif
 };
 
···
 				     const u8 *raw_key,
 				     const struct fscrypt_info *ci);
 
-void fscrypt_destroy_inline_crypt_key(struct fscrypt_prepared_key *prep_key);
+void fscrypt_destroy_inline_crypt_key(struct super_block *sb,
+				      struct fscrypt_prepared_key *prep_key);
 
 /*
  * Check whether the crypto transform or blk-crypto key has been allocated in
···
 }
 
 static inline void
-fscrypt_destroy_inline_crypt_key(struct fscrypt_prepared_key *prep_key)
+fscrypt_destroy_inline_crypt_key(struct super_block *sb,
+				 struct fscrypt_prepared_key *prep_key)
 {
 }
 
···
 int fscrypt_prepare_key(struct fscrypt_prepared_key *prep_key,
 			const u8 *raw_key, const struct fscrypt_info *ci);
 
-void fscrypt_destroy_prepared_key(struct fscrypt_prepared_key *prep_key);
+void fscrypt_destroy_prepared_key(struct super_block *sb,
+				  struct fscrypt_prepared_key *prep_key);
 
 int fscrypt_set_per_file_enc_key(struct fscrypt_info *ci, const u8 *raw_key);
 

fs/crypto/inline_crypt.c

···
 
 #include "fscrypt_private.h"
 
-struct fscrypt_blk_crypto_key {
-	struct blk_crypto_key base;
-	int num_devs;
-	struct request_queue *devs[];
-};
-
 static int fscrypt_get_num_devices(struct super_block *sb)
 {
 	if (sb->s_cop->get_num_devices)
···
 	const struct inode *inode = ci->ci_inode;
 	struct super_block *sb = inode->i_sb;
 	enum blk_crypto_mode_num crypto_mode = ci->ci_mode->blk_crypto_mode;
-	int num_devs = fscrypt_get_num_devices(sb);
-	int queue_refs = 0;
-	struct fscrypt_blk_crypto_key *blk_key;
+	struct blk_crypto_key *blk_key;
+	struct request_queue **devs;
+	unsigned int num_devs;
+	unsigned int i;
 	int err;
-	int i;
 
-	blk_key = kzalloc(struct_size(blk_key, devs, num_devs), GFP_KERNEL);
+	blk_key = kmalloc(sizeof(*blk_key), GFP_KERNEL);
 	if (!blk_key)
 		return -ENOMEM;
 
-	blk_key->num_devs = num_devs;
-	fscrypt_get_devices(sb, num_devs, blk_key->devs);
-
-	err = blk_crypto_init_key(&blk_key->base, raw_key, crypto_mode,
+	err = blk_crypto_init_key(blk_key, raw_key, crypto_mode,
 				  fscrypt_get_dun_bytes(ci), sb->s_blocksize);
 	if (err) {
 		fscrypt_err(inode, "error %d initializing blk-crypto key", err);
 		goto fail;
 	}
 
-	/*
-	 * We have to start using blk-crypto on all the filesystem's devices.
-	 * We also have to save all the request_queue's for later so that the
-	 * key can be evicted from them.  This is needed because some keys
-	 * aren't destroyed until after the filesystem was already unmounted
-	 * (namely, the per-mode keys in struct fscrypt_master_key).
-	 */
-	for (i = 0; i < num_devs; i++) {
-		if (!blk_get_queue(blk_key->devs[i])) {
-			fscrypt_err(inode, "couldn't get request_queue");
-			err = -EAGAIN;
-			goto fail;
-		}
-		queue_refs++;
-
-		err = blk_crypto_start_using_key(&blk_key->base,
-						 blk_key->devs[i]);
-		if (err) {
-			fscrypt_err(inode,
-				    "error %d starting to use blk-crypto", err);
-			goto fail;
-		}
+	/* Start using blk-crypto on all the filesystem's block devices. */
+	num_devs = fscrypt_get_num_devices(sb);
+	devs = kmalloc_array(num_devs, sizeof(*devs), GFP_KERNEL);
+	if (!devs) {
+		err = -ENOMEM;
+		goto fail;
 	}
+	fscrypt_get_devices(sb, num_devs, devs);
+	for (i = 0; i < num_devs; i++) {
+		err = blk_crypto_start_using_key(blk_key, devs[i]);
+		if (err)
+			break;
+	}
+	kfree(devs);
+	if (err) {
+		fscrypt_err(inode, "error %d starting to use blk-crypto", err);
+		goto fail;
+	}
+
 	/*
 	 * Pairs with the smp_load_acquire() in fscrypt_is_key_prepared().
 	 * I.e., here we publish ->blk_key with a RELEASE barrier so that
···
 	return 0;
 
 fail:
-	for (i = 0; i < queue_refs; i++)
-		blk_put_queue(blk_key->devs[i]);
 	kfree_sensitive(blk_key);
 	return err;
 }
 
-void fscrypt_destroy_inline_crypt_key(struct fscrypt_prepared_key *prep_key)
+void fscrypt_destroy_inline_crypt_key(struct super_block *sb,
+				      struct fscrypt_prepared_key *prep_key)
 {
-	struct fscrypt_blk_crypto_key *blk_key = prep_key->blk_key;
-	int i;
+	struct blk_crypto_key *blk_key = prep_key->blk_key;
+	struct request_queue **devs;
+	unsigned int num_devs;
+	unsigned int i;
 
-	if (blk_key) {
-		for (i = 0; i < blk_key->num_devs; i++) {
-			blk_crypto_evict_key(blk_key->devs[i], &blk_key->base);
-			blk_put_queue(blk_key->devs[i]);
-		}
-		kfree_sensitive(blk_key);
+	if (!blk_key)
+		return;
+
+	/* Evict the key from all the filesystem's block devices. */
+	num_devs = fscrypt_get_num_devices(sb);
+	devs = kmalloc_array(num_devs, sizeof(*devs), GFP_KERNEL);
+	if (devs) {
+		fscrypt_get_devices(sb, num_devs, devs);
+		for (i = 0; i < num_devs; i++)
+			blk_crypto_evict_key(devs[i], blk_key);
+		kfree(devs);
 	}
+	kfree_sensitive(blk_key);
 }
 
 bool __fscrypt_inode_uses_inline_crypto(const struct inode *inode)
···
 	ci = inode->i_crypt_info;
 
 	fscrypt_generate_dun(ci, first_lblk, dun);
-	bio_crypt_set_ctx(bio, &ci->ci_enc_key.blk_key->base, dun, gfp_mask);
+	bio_crypt_set_ctx(bio, ci->ci_enc_key.blk_key, dun, gfp_mask);
 }
 EXPORT_SYMBOL_GPL(fscrypt_set_bio_crypt_ctx);
 
···
 	 * uses the same pointer.  I.e., there's currently no need to support
 	 * merging requests where the keys are the same but the pointers differ.
 	 */
-	if (bc->bc_key != &inode->i_crypt_info->ci_enc_key.blk_key->base)
+	if (bc->bc_key != inode->i_crypt_info->ci_enc_key.blk_key)
 		return false;
 
 	fscrypt_generate_dun(inode->i_crypt_info, next_lblk, next_dun);

fs/crypto/keyring.c

···
 	WARN_ON(!list_empty(&mk->mk_decrypted_inodes));
 
 	for (i = 0; i <= FSCRYPT_MODE_MAX; i++) {
-		fscrypt_destroy_prepared_key(&mk->mk_direct_keys[i]);
-		fscrypt_destroy_prepared_key(&mk->mk_iv_ino_lblk_64_keys[i]);
-		fscrypt_destroy_prepared_key(&mk->mk_iv_ino_lblk_32_keys[i]);
+		fscrypt_destroy_prepared_key(
+				sb, &mk->mk_direct_keys[i]);
+		fscrypt_destroy_prepared_key(
+				sb, &mk->mk_iv_ino_lblk_64_keys[i]);
+		fscrypt_destroy_prepared_key(
+				sb, &mk->mk_iv_ino_lblk_32_keys[i]);
 	}
 	memzero_explicit(&mk->mk_ino_hash_key,
 			 sizeof(mk->mk_ino_hash_key));

fs/crypto/keysetup.c

···
 }
 
 /* Destroy a crypto transform object and/or blk-crypto key. */
-void fscrypt_destroy_prepared_key(struct fscrypt_prepared_key *prep_key)
+void fscrypt_destroy_prepared_key(struct super_block *sb,
+				  struct fscrypt_prepared_key *prep_key)
 {
 	crypto_free_skcipher(prep_key->tfm);
-	fscrypt_destroy_inline_crypt_key(prep_key);
+	fscrypt_destroy_inline_crypt_key(sb, prep_key);
 	memzero_explicit(prep_key, sizeof(*prep_key));
 }
 
···
 	if (ci->ci_direct_key)
 		fscrypt_put_direct_key(ci->ci_direct_key);
 	else if (ci->ci_owns_key)
-		fscrypt_destroy_prepared_key(&ci->ci_enc_key);
+		fscrypt_destroy_prepared_key(ci->ci_inode->i_sb,
+					     &ci->ci_enc_key);
 
 	mk = ci->ci_master_key;
 	if (mk) {

fs/crypto/keysetup_v1.c

···
 
 /* Master key referenced by DIRECT_KEY policy */
 struct fscrypt_direct_key {
+	struct super_block		*dk_sb;
 	struct hlist_node		dk_node;
 	refcount_t			dk_refcount;
 	const struct fscrypt_mode	*dk_mode;
···
 static void free_direct_key(struct fscrypt_direct_key *dk)
 {
 	if (dk) {
-		fscrypt_destroy_prepared_key(&dk->dk_key);
+		fscrypt_destroy_prepared_key(dk->dk_sb, &dk->dk_key);
 		kfree_sensitive(dk);
 	}
 }
···
 	dk = kzalloc(sizeof(*dk), GFP_KERNEL);
 	if (!dk)
 		return ERR_PTR(-ENOMEM);
+	dk->dk_sb = ci->ci_inode->i_sb;
 	refcount_set(&dk->dk_refcount, 1);
 	dk->dk_mode = ci->ci_mode;
 	err = fscrypt_prepare_key(&dk->dk_key, raw_key, ci);