fscrypto: require write access to mount to set encryption policy

[cascardo/linux.git] / fs / crypto / policy.c

diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c
index f96547f..ed115ac 100644 (file)
--- a/fs/crypto/policy.c
+++ b/fs/crypto/policy.c
@@ -11,6 +11,7 @@
 #include <linux/random.h>
 #include <linux/string.h>
 #include <linux/fscrypto.h>
+#include <linux/mount.h>
 
 static int inode_has_encryption_context(struct inode *inode)
 {
@@ -92,31 +93,42 @@ static int create_encryption_context_from_policy(struct inode *inode,
        return inode->i_sb->s_cop->set_context(inode, &ctx, sizeof(ctx), NULL);
 }
 
-int fscrypt_process_policy(struct inode *inode,
+int fscrypt_process_policy(struct file *filp,
                                const struct fscrypt_policy *policy)
 {
+       struct inode *inode = file_inode(filp);
+       int ret;
+
        if (!inode_owner_or_capable(inode))
                return -EACCES;
 
        if (policy->version != 0)
                return -EINVAL;
 
+       ret = mnt_want_write_file(filp);
+       if (ret)
+               return ret;
+
        if (!inode_has_encryption_context(inode)) {
                if (!S_ISDIR(inode->i_mode))
-                       return -EINVAL;
-               if (!inode->i_sb->s_cop->empty_dir)
-                       return -EOPNOTSUPP;
-               if (!inode->i_sb->s_cop->empty_dir(inode))
-                       return -ENOTEMPTY;
-               return create_encryption_context_from_policy(inode, policy);
+                       ret = -EINVAL;
+               else if (!inode->i_sb->s_cop->empty_dir)
+                       ret = -EOPNOTSUPP;
+               else if (!inode->i_sb->s_cop->empty_dir(inode))
+                       ret = -ENOTEMPTY;
+               else
+                       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;
        }
 
-       if (is_encryption_context_consistent_with_policy(inode, policy))
-               return 0;
-
-       printk(KERN_WARNING "%s: Policy inconsistent with encryption context\n",
-              __func__);
-       return -EINVAL;
+       mnt_drop_write_file(filp);
+       return ret;
 }
 EXPORT_SYMBOL(fscrypt_process_policy);