ext4 crypto: use dget_parent() in ext4_d_revalidate()

This avoids potential problems caused by a race where the inode gets
renamed out from its parent directory and the parent directory is
deleted while ext4_d_revalidate() is running.

Fixes: 28b4c263961c
Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org

diff --git a/fs/ext4/crypto.c b/fs/ext4/crypto.c
index 012fd3285147d6b225767cd754ecd20e280cf54c..ea69ce4f6d8f71bef001356ffcf8941f79fc0aef 100644 (file)
--- a/fs/ext4/crypto.c
+++ b/fs/ext4/crypto.c
@@ -478,13 +478,16 @@ uint32_t ext4_validate_encryption_key_size(uint32_t mode, uint32_t size)
  */
 static int ext4_d_revalidate(struct dentry *dentry, unsigned int flags)
 {
-       struct inode *dir = d_inode(dentry->d_parent);
-       struct ext4_crypt_info *ci = EXT4_I(dir)->i_crypt_info;
+       struct dentry *dir;
+       struct ext4_crypt_info *ci;
        int dir_has_key, cached_with_key;
 
-       if (!ext4_encrypted_inode(dir))
+       dir = dget_parent(dentry);
+       if (!ext4_encrypted_inode(d_inode(dir))) {
+               dput(dir);
                return 0;
-
+       }
+       ci = EXT4_I(d_inode(dir))->i_crypt_info;
        if (ci && ci->ci_keyring_key &&
            (ci->ci_keyring_key->flags & ((1 << KEY_FLAG_INVALIDATED) |
                                          (1 << KEY_FLAG_REVOKED) |
@@ -494,6 +497,7 @@ static int ext4_d_revalidate(struct dentry *dentry, unsigned int flags)
        /* this should eventually be an flag in d_flags */
        cached_with_key = dentry->d_fsdata != NULL;
        dir_has_key = (ci != NULL);
+       dput(dir);
 
        /*
         * If the dentry was cached without the key, and it is a