linux-ext4 - [PATCH v2 07/11] fscrypt: require that fscrypt_encrypt

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Date:   Sun, 13 Sep 2020 01:36:16 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     linux-fscrypt@...r.kernel.org
Cc:     linux-ext4@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net,
        linux-mtd@...ts.infradead.org, ceph-devel@...r.kernel.org,
        Jeff Layton <jlayton@...nel.org>,
        Daniel Rosenberg <drosen@...gle.com>
Subject: [PATCH v2 07/11] fscrypt: require that fscrypt_encrypt_symlink() already has key

From: Eric Biggers <ebiggers@...gle.com>

Now that all filesystems have been converted to use
fscrypt_prepare_new_inode(), the encryption key for new symlink inodes
is now already set up whenever we try to encrypt the symlink target.
Enforce this rather than try to set up the key again when it may be too
late to do so safely.

Signed-off-by: Eric Biggers <ebiggers@...gle.com>
---
 fs/crypto/hooks.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/crypto/hooks.c b/fs/crypto/hooks.c
index 491b252843eb9..7748db5092409 100644
--- a/fs/crypto/hooks.c
+++ b/fs/crypto/hooks.c
@@ -217,9 +217,13 @@ int __fscrypt_encrypt_symlink(struct inode *inode, const char *target,
 	struct fscrypt_symlink_data *sd;
 	unsigned int ciphertext_len;
 
-	err = fscrypt_require_key(inode);
-	if (err)
-		return err;
+	/*
+	 * fscrypt_prepare_new_inode() should have already set up the new
+	 * symlink inode's encryption key.  We don't wait until now to do it,
+	 * since we may be in a filesystem transaction now.
+	 */
+	if (WARN_ON_ONCE(!fscrypt_has_encryption_key(inode)))
+		return -ENOKEY;
 
 	if (disk_link->name) {
 		/* filesystem-provided buffer */
-- 
2.28.0