Commit 9dd78d8c authored by Miklos Szeredi's avatar Miklos Szeredi Committed by Theodore Ts'o
Browse files

ext4: use dget_parent() in ext4_file_open() 



In f_op->open() lock on parent is not held, so there's no guarantee that
parent dentry won't go away at any time.

Even after this patch there's no guarantee that 'dir' will stay the parent
of 'inode', but at least it won't be freed while being used.

Fixes: ff978b09 ("ext4 crypto: move context consistency check to ext4_file_open()")
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
Cc: <stable@vger.kernel.org> # v4.5
parent be62a1a8

fs/ext4/file.c

+8 −4
Original line number Diff line number Diff line
@@ -329,7 +329,7 @@ static int ext4_file_open(struct inode * inode, struct file * filp) 
	struct super_block *sb = inode->i_sb;

	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);

	struct vfsmount *mnt = filp->f_path.mnt;

	struct inode *dir = filp->f_path.dentry->d_parent->d_inode;

	struct dentry *dir;

	struct path path;

	char buf[64], *cp;

	int ret;
@@ -373,14 +373,18 @@ static int ext4_file_open(struct inode * inode, struct file * filp) 
		if (ext4_encryption_info(inode) == NULL)

			return -ENOKEY;

	}

	if (ext4_encrypted_inode(dir) &&

	    !ext4_is_child_context_consistent_with_parent(dir, inode)) {



	dir = dget_parent(filp->f_path.dentry);

	if (ext4_encrypted_inode(d_inode(dir)) &&

	    !ext4_is_child_context_consistent_with_parent(d_inode(dir), inode)) {

		ext4_warning(inode->i_sb,

			     "Inconsistent encryption contexts: %lu/%lu\n",

			     (unsigned long) dir->i_ino,

			     (unsigned long) d_inode(dir)->i_ino,

			     (unsigned long) inode->i_ino);

		dput(dir);

		return -EPERM;

	}

	dput(dir);

	/*

	 * Set up the jbd2_inode if we are opening the inode for

	 * writing and the journal is present

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