[RFC PATCH v5 04/19] fscrypt: add fscrypt_context_for_new_inode

Jeff Layton
2021-03-26T17:33:14Z

CephFS will need to be able to generate a context for a new "prepared"
inode. Add a new routine for getting the context out of an in-core
inode.

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