[PATCH 2/3] f2fs: use dget_parent and file_dentry in f2fs_file_open

[Jaegeuk Kim]

This patch synced with the below two ext4 crypto fixes together.

In 4.6-rc1, f2fs newly introduced accessing f_path.dentry which crashes
overlayfs. To fix, now we need to use file_dentry() to access that field.

Fixes: c0a37d487884 ("ext4: use file_dentry()")
Fixes: 9dd78d8c9a7b ("ext4: use dget_parent() in ext4_file_open()")
Cc: Miklos Szeredi <mszer...@redhat.com>
Cc: Theodore Ts'o <ty...@mit.edu>
Signed-off-by: Jaegeuk Kim <jaeg...@kernel.org>
---
 fs/f2fs/file.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 443e077..90d1157 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -441,7 +441,7 @@ static int f2fs_file_mmap(struct file *file, struct 
vm_area_struct *vma)
 static int f2fs_file_open(struct inode *inode, struct file *filp)
 {
        int ret = generic_file_open(inode, filp);
-       struct inode *dir = filp->f_path.dentry->d_parent->d_inode;
+       struct dentry *dir;
 
        if (!ret && f2fs_encrypted_inode(inode)) {
                ret = fscrypt_get_encryption_info(inode);
@@ -450,9 +450,13 @@ static int f2fs_file_open(struct inode *inode, struct file 
*filp)
                if (!fscrypt_has_encryption_key(inode))
                        return -ENOKEY;
        }
-       if (f2fs_encrypted_inode(dir) &&
-                       !fscrypt_has_permitted_context(dir, inode))
+       dir = dget_parent(file_dentry(filp));
+       if (f2fs_encrypted_inode(d_inode(dir)) &&
+                       !fscrypt_has_permitted_context(d_inode(dir), inode)) {
+               dput(dir);
                return -EPERM;
+       }
+       dput(dir);
        return ret;
 }
 
-- 
2.6.3