[PATCH v3 07/16] fscrypt: use an optional ino equivalent for per-extent infos

[Sweet Tea Dorminy <sweettea-kernel@xxxxxxxxxx>]

Since per-extent infos are not tied to inodes, an ino-based policy
cannot access the inode's i_ino to get the necessary information.
Instead, this adds an optional fscrypt_operation pointer to get the ino
equivalent for an extent, adds a wrapper to get the ino for an info, and
uses this wrapper everywhere where the ci's inode's i_ino is currently
accessed.

Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@xxxxxxxxxx>
---
 fs/crypto/fscrypt_private.h | 18 ++++++++++++++++++
 fs/crypto/keyring.c         |  8 ++++----
 fs/crypto/keysetup.c        |  6 +++---
 include/linux/fscrypt.h     |  9 +++++++++
 4 files changed, 34 insertions(+), 7 deletions(-)

diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
index 1244797cd8a9..4fe79b774f1f 100644
--- a/fs/crypto/fscrypt_private.h
+++ b/fs/crypto/fscrypt_private.h
@@ -332,6 +332,24 @@ static inline bool fscrypt_uses_extent_encryption(const struct inode *inode)
 	return false;
 }
 
+/**
+ * fscrypt_get_info_ino() - get the ino or ino equivalent for an info
+ *
+ * @ci: the fscrypt_info in question
+ *
+ * Return: For inode-based encryption, this will return the info's inode's ino.
+ * For extent-based encryption, this will return the extent's ino equivalent
+ * or 0 if it is not implemented.
+ */
+static inline u64 fscrypt_get_info_ino(const struct fscrypt_info *ci)
+{
+	if (ci->ci_inode)
+		return ci->ci_inode->i_ino;
+	if (!ci->ci_sb->s_cop->get_extent_ino_equivalent)
+		return 0;
+	return ci->ci_sb->s_cop->get_extent_ino_equivalent(ci->ci_info_ptr);
+}
+
 /* crypto.c */
 extern struct kmem_cache *fscrypt_info_cachep;
 int fscrypt_initialize(struct super_block *sb);
diff --git a/fs/crypto/keyring.c b/fs/crypto/keyring.c
index 7cbb1fd872ac..53e37b8a822c 100644
--- a/fs/crypto/keyring.c
+++ b/fs/crypto/keyring.c
@@ -914,12 +914,12 @@ static int check_for_busy_inodes(struct super_block *sb,
 	}
 
 	{
-		/* select an example file to show for debugging purposes */
-		struct inode *inode =
+		/* select an example info to show for debugging purposes */
+		struct fscrypt_info *ci =
 			list_first_entry(&mk->mk_decrypted_inodes,
 					 struct fscrypt_info,
-					 ci_master_key_link)->ci_inode;
-		ino = inode->i_ino;
+					 ci_master_key_link);
+		ino = fscrypt_get_info_ino(ci);
 	}
 	spin_unlock(&mk->mk_decrypted_inodes_lock);
 
diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
index c72f9015ed35..32e62cc57708 100644
--- a/fs/crypto/keysetup.c
+++ b/fs/crypto/keysetup.c
@@ -380,10 +380,10 @@ int fscrypt_derive_dirhash_key(struct fscrypt_info *ci,
 void fscrypt_hash_inode_number(struct fscrypt_info *ci,
 			       const struct fscrypt_master_key *mk)
 {
-	WARN_ON_ONCE(ci->ci_inode->i_ino == 0);
+	WARN_ON_ONCE(fscrypt_get_info_ino(ci) == 0);
 	WARN_ON_ONCE(!mk->mk_ino_hash_key_initialized);
 
-	ci->ci_hashed_ino = (u32)siphash_1u64(ci->ci_inode->i_ino,
+	ci->ci_hashed_ino = (u32)siphash_1u64(fscrypt_get_info_ino(ci),
 					      &mk->mk_ino_hash_key);
 }
 
@@ -705,7 +705,7 @@ fscrypt_setup_encryption_info(struct inode *inode,
 		if (res)
 			goto out;
 
-		if (inode->i_ino)
+		if (fscrypt_get_info_ino(crypt_info))
 			fscrypt_hash_inode_number(crypt_info, mk);
 	}
 
diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index c895b12737a1..2a64e7a71a53 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -160,6 +160,15 @@ struct fscrypt_operations {
 	void (*get_ino_and_lblk_bits)(struct super_block *sb,
 				      int *ino_bits_ret, int *lblk_bits_ret);
 
+	/*
+	 * Get the inode number equivalent for filesystems using per-extent
+	 * encryption keys.
+	 *
+	 * This function only needs to be implemented if support for one of the
+	 * FSCRYPT_POLICY_FLAG_IV_INO_* flags is needed.
+	 */
+	u64 (*get_extent_ino_equivalent)(struct fscrypt_info **info_ptr);
+
 	/*
 	 * Return an array of pointers to the block devices to which the
 	 * filesystem may write encrypted file contents, NULL if the filesystem
-- 
2.41.0