In some cases, the previous code did not correctly propagate errors to
the caller. Also, only one call to ->get_context() is required.
Signed-off-by: Eric Biggers <ebigge...@gmail.com>
---
fs/crypto/policy.c | 64 +++++++++++++++++++++++++-----------------------------
1 file changed, 29 insertions(+), 35 deletions(-)
diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c
index 6a767e6..83421fe 100644
--- a/fs/crypto/policy.c
+++ b/fs/crypto/policy.c
@@ -13,37 +13,17 @@
#include <linux/fscrypto.h>
#include <linux/mount.h>
-static bool inode_has_encryption_context(struct inode *inode)
-{
- if (!inode->i_sb->s_cop->get_context)
- return false;
- return (inode->i_sb->s_cop->get_context(inode, NULL, 0L) > 0);
-}
-
-/*
- * check whether the policy is consistent with the encryption context
- * for the inode
- */
-static bool is_encryption_context_consistent_with_policy(struct inode *inode,
+static bool is_encryption_context_consistent_with_policy(
+ const struct fscrypt_context *ctx,
const struct fscrypt_policy *policy)
{
- struct fscrypt_context ctx;
- int res;
-
- if (!inode->i_sb->s_cop->get_context)
- return false;
-
- res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
- if (res != sizeof(ctx))
- return false;
-
- return (memcmp(ctx.master_key_descriptor, policy->master_key_descriptor,
- FS_KEY_DESCRIPTOR_SIZE) == 0 &&
- (ctx.flags == policy->flags) &&
- (ctx.contents_encryption_mode ==
- policy->contents_encryption_mode) &&
- (ctx.filenames_encryption_mode ==
- policy->filenames_encryption_mode));
+ return memcmp(ctx->master_key_descriptor, policy->master_key_descriptor,
+ FS_KEY_DESCRIPTOR_SIZE) == 0 &&
+ (ctx->flags == policy->flags) &&
+ (ctx->contents_encryption_mode ==
+ policy->contents_encryption_mode) &&
+ (ctx->filenames_encryption_mode ==
+ policy->filenames_encryption_mode);
}
static int create_encryption_context_from_policy(struct inode *inode,
@@ -96,6 +76,7 @@ static int create_encryption_context_from_policy(struct inode
*inode,
int fscrypt_set_policy(struct file *file, const struct fscrypt_policy *policy)
{
struct inode *inode = file_inode(file);
+ struct fscrypt_context existing;
int ret;
if (!inode_owner_or_capable(inode))
@@ -110,7 +91,25 @@ int fscrypt_set_policy(struct file *file, const struct
fscrypt_policy *policy)
inode_lock(inode);
- if (!inode_has_encryption_context(inode)) {
+ ret = -ENODATA;
+ if (inode->i_sb->s_cop->get_context) {
+ ret = inode->i_sb->s_cop->get_context(inode, &existing,
+ sizeof(existing));
+ }
+ if (ret != -ENODATA) {
+ /* An existing policy cannot be changed. However, an attempt to
+ * set an identical policy will succeed. */
+ if (ret == sizeof(existing) &&
+ is_encryption_context_consistent_with_policy(&existing,
+ policy)) {
+ ret = 0;
+ } else if (ret >= 0 || ret == -ERANGE) {
+ printk(KERN_WARNING
+ "%s: Policy inconsistent with encryption
context\n",
+ __func__);
+ ret = -EINVAL;
+ }
+ } else {
/* A new policy may only be set on an empty directory or an
* empty regular file. */
ret = -EINVAL;
@@ -130,11 +129,6 @@ int fscrypt_set_policy(struct file *file, const struct
fscrypt_policy *policy)
ret = create_encryption_context_from_policy(inode,
policy);
}
- } else if (!is_encryption_context_consistent_with_policy(inode,
policy)) {
- printk(KERN_WARNING
- "%s: Policy inconsistent with encryption context\n",
- __func__);
- ret = -EINVAL;
}
inode_unlock(inode);
mnt_drop_write_file(file);
--
2.7.4
