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From: Jeff Layton <jlayton@kernel.org>
To: ceph-devel@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org, linux-fscrypt@vger.kernel.org,
	lhenriques@suse.de
Subject: [RFC PATCH v6 04/20] fscrypt: add fscrypt_context_for_new_inode
Date: Tue, 13 Apr 2021 13:50:36 -0400
Message-ID: <20210413175052.163865-5-jlayton@kernel.org> (raw)
In-Reply-To: <20210413175052.163865-1-jlayton@kernel.org>

Most filesystems just call fscrypt_set_context on new inodes, which
usually causes a setxattr. That's a bit late for ceph, which can send
along a full blob of xattrs with the create request.

That allows us to avoid race windows that where the new inode could be
seen by other clients without the crypto context attached. It also
avoids the separate round trip to the server.

Refactor the code a bit to allow us to create a new crypto context,
attach it to the inode, and write it to the buffer, but without calling
set_context on it. ceph can later use this to marshal the context into
the buffer we send along with the create request.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 fs/crypto/policy.c      | 34 ++++++++++++++++++++++++++++------
 include/linux/fscrypt.h |  1 +
 2 files changed, 29 insertions(+), 6 deletions(-)

diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c
index ed3d623724cd..6a895a31560f 100644
--- a/fs/crypto/policy.c
+++ b/fs/crypto/policy.c
@@ -664,6 +664,31 @@ const union fscrypt_policy *fscrypt_policy_to_inherit(struct inode *dir)
 	return fscrypt_get_dummy_policy(dir->i_sb);
 }
 
+/**
+ * fscrypt_context_for_new_inode() - create an encryption context for a new inode
+ * @ctx: where context should be written
+ * @inode: inode from which to fetch policy and nonce
+ *
+ * Given an in-core "prepared" (via fscrypt_prepare_new_inode) inode,
+ * generate a new context and write it to ctx. ctx _must_ be at least
+ * FSCRYPT_SET_CONTEXT_MAX_SIZE bytes.
+ *
+ * Returns size of the resulting context or a negative error code.
+ */
+int fscrypt_context_for_new_inode(void *ctx, struct inode *inode)
+{
+	struct fscrypt_info *ci = inode->i_crypt_info;
+
+	BUILD_BUG_ON(sizeof(union fscrypt_context) != FSCRYPT_SET_CONTEXT_MAX_SIZE);
+
+	/* fscrypt_prepare_new_inode() should have set up the key already. */
+	if (WARN_ON_ONCE(!ci))
+		return -ENOKEY;
+
+	return fscrypt_new_context(ctx, &ci->ci_policy, ci->ci_nonce);
+}
+EXPORT_SYMBOL_GPL(fscrypt_context_for_new_inode);
+
 /**
  * fscrypt_set_context() - Set the fscrypt context of a new inode
  * @inode: a new inode
@@ -680,12 +705,9 @@ int fscrypt_set_context(struct inode *inode, void *fs_data)
 	union fscrypt_context ctx;
 	int ctxsize;
 
-	/* fscrypt_prepare_new_inode() should have set up the key already. */
-	if (WARN_ON_ONCE(!ci))
-		return -ENOKEY;
-
-	BUILD_BUG_ON(sizeof(ctx) != FSCRYPT_SET_CONTEXT_MAX_SIZE);
-	ctxsize = fscrypt_new_context(&ctx, &ci->ci_policy, ci->ci_nonce);
+	ctxsize = fscrypt_context_for_new_inode(&ctx, inode);
+	if (ctxsize < 0)
+		return ctxsize;
 
 	/*
 	 * This may be the first time the inode number is available, so do any
diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index b5c31baaa8bf..087fa87bca0b 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -178,6 +178,7 @@ int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg);
 int fscrypt_ioctl_get_policy_ex(struct file *filp, void __user *arg);
 int fscrypt_ioctl_get_nonce(struct file *filp, void __user *arg);
 int fscrypt_has_permitted_context(struct inode *parent, struct inode *child);
+int fscrypt_context_for_new_inode(void *ctx, struct inode *inode);
 int fscrypt_set_context(struct inode *inode, void *fs_data);
 
 struct fscrypt_dummy_policy {
-- 
2.30.2


  parent reply index

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-13 17:50 [RFC PATCH v6 00/20] ceph+fscrypt: context, filename and symlink support Jeff Layton
2021-04-13 17:50 ` [RFC PATCH v6 01/20] vfs: export new_inode_pseudo Jeff Layton
2021-04-13 17:50 ` [RFC PATCH v6 02/20] fscrypt: export fscrypt_base64_encode and fscrypt_base64_decode Jeff Layton
2021-04-13 17:50 ` [RFC PATCH v6 03/20] fscrypt: export fscrypt_fname_encrypt and fscrypt_fname_encrypted_size Jeff Layton
2021-04-13 17:50 ` Jeff Layton [this message]
2021-04-13 17:50 ` [RFC PATCH v6 05/20] ceph: crypto context handling for ceph Jeff Layton
2021-04-13 17:50 ` [RFC PATCH v6 06/20] ceph: implement -o test_dummy_encryption mount option Jeff Layton
2021-04-13 17:50 ` [RFC PATCH v6 07/20] ceph: preallocate inode for ops that may create one Jeff Layton
2021-04-13 17:50 ` [RFC PATCH v6 08/20] ceph: add routine to create fscrypt context prior to RPC Jeff Layton
2021-04-13 17:50 ` [RFC PATCH v6 09/20] ceph: make ceph_msdc_build_path use ref-walk Jeff Layton
2021-04-13 17:50 ` [RFC PATCH v6 10/20] ceph: add encrypted fname handling to ceph_mdsc_build_path Jeff Layton
2021-04-13 17:50 ` [RFC PATCH v6 11/20] ceph: decode alternate_name in lease info Jeff Layton
2021-04-13 17:50 ` [RFC PATCH v6 12/20] ceph: send altname in MClientRequest Jeff Layton
2021-04-13 17:50 ` [RFC PATCH v6 13/20] ceph: properly set DCACHE_NOKEY_NAME flag in lookup Jeff Layton
2021-04-13 17:50 ` [RFC PATCH v6 14/20] ceph: make d_revalidate call fscrypt revalidator for encrypted dentries Jeff Layton
2021-04-13 17:50 ` [RFC PATCH v6 15/20] ceph: add helpers for converting names for userland presentation Jeff Layton
2021-04-13 17:50 ` [RFC PATCH v6 16/20] ceph: add fscrypt support to ceph_fill_trace Jeff Layton
2021-04-13 17:50 ` [RFC PATCH v6 17/20] ceph: add support to readdir for encrypted filenames Jeff Layton
2021-04-13 17:50 ` [RFC PATCH v6 18/20] ceph: create symlinks with encrypted and base64-encoded targets Jeff Layton
2021-04-13 17:50 ` [RFC PATCH v6 19/20] ceph: make ceph_get_name decrypt filenames Jeff Layton
2021-04-13 17:50 ` [RFC PATCH v6 20/20] ceph: add fscrypt ioctls Jeff Layton
2021-04-19 10:09   ` Luis Henriques
2021-04-19 12:19     ` Jeff Layton
2021-04-19 19:54       ` Eric Biggers
2021-04-20  9:34         ` Luis Henriques
2021-04-20 11:45         ` Jeff Layton
2021-04-19 10:30 ` [RFC PATCH v6 00/20] ceph+fscrypt: context, filename and symlink support Luis Henriques
2021-04-19 12:23   ` Jeff Layton
2021-04-19 16:03     ` Luis Henriques
2021-04-19 16:28       ` Jeff Layton
2021-04-20 10:11         ` Luis Henriques
2021-04-20 15:52           ` Jeff Layton

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