Merge tag 'for_linus_stable' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4

Pull fscrypto fixes fromTed Ts'o:
 "Fix some brown-paper-bag bugs for fscrypto, including one one which
  allows a malicious user to set an encryption policy on an empty
  directory which they do not own"

* tag 'for_linus_stable' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4:
  fscrypto: require write access to mount to set encryption policy
  fscrypto: only allow setting encryption policy on directories
  fscrypto: add authorization check for setting encryption policy

4 files changed, 33 insertions, 24 deletions

diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c
index 0f9961eede1e..ed115acb5dee 100644
--- 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)
 {
@@ -92,26 +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 (!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);
+                if (!S_ISDIR(inode->i_mode))
+                        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);
 
diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index 10686fd67fb4..1bb7df5e4536 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -776,7 +776,7 @@ resizefs_out:
                                    (struct fscrypt_policy __user *)arg,
                                    sizeof(policy)))
                         return -EFAULT;
-                return fscrypt_process_policy(inode, &policy);
+                return fscrypt_process_policy(filp, &policy);
 #else
                 return -EOPNOTSUPP;
 #endif
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 47abb96098e4..28f4f4cbb8d8 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1757,21 +1757,14 @@ static int f2fs_ioc_set_encryption_policy(struct file *filp, unsigned long arg)
 {
         struct fscrypt_policy policy;
         struct inode *inode = file_inode(filp);
-        int ret;
 
         if (copy_from_user(&policy, (struct fscrypt_policy __user *)arg,
                                                         sizeof(policy)))
                 return -EFAULT;
 
-        ret = mnt_want_write_file(filp);
-        if (ret)
-                return ret;
-
         f2fs_update_time(F2FS_I_SB(inode), REQ_TIME);
-        ret = fscrypt_process_policy(inode, &policy);
 
-        mnt_drop_write_file(filp);
-        return ret;
+        return fscrypt_process_policy(filp, &policy);
 }
 
 static int f2fs_ioc_get_encryption_policy(struct file *filp, unsigned long arg)
diff --git a/include/linux/fscrypto.h b/include/linux/fscrypto.h
index cfa6cde25f8e..76cff18bb032 100644
--- a/include/linux/fscrypto.h
+++ b/include/linux/fscrypto.h
@@ -274,8 +274,7 @@ extern void fscrypt_restore_control_page(struct page *);
 extern int fscrypt_zeroout_range(struct inode *, pgoff_t, sector_t,
                                                 unsigned int);
 /* policy.c */
-extern int fscrypt_process_policy(struct inode *,
-                                        const struct fscrypt_policy *);
+extern int fscrypt_process_policy(struct file *, const struct fscrypt_policy *);
 extern int fscrypt_get_policy(struct inode *, struct fscrypt_policy *);
 extern int fscrypt_has_permitted_context(struct inode *, struct inode *);
 extern int fscrypt_inherit_context(struct inode *, struct inode *,
@@ -345,7 +344,7 @@ static inline int fscrypt_notsupp_zeroout_range(struct inode *i, pgoff_t p,
 }
 
 /* policy.c */
-static inline int fscrypt_notsupp_process_policy(struct inode *i,
+static inline int fscrypt_notsupp_process_policy(struct file *f,
                                 const struct fscrypt_policy *p)
 {
         return -EOPNOTSUPP;