linux-kernel - [PATCH 10/16] Unionfs: create opaque directories' whiteouts unconditionally

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Date:	Mon, 26 Nov 2007 11:44:07 -0500
From:	Erez Zadok <ezk@...sunysb.edu>
To:	akpm@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	viro@....linux.org.uk, hch@...radead.org,
	Erez Zadok <ezk@...sunysb.edu>
Subject: [PATCH 10/16] Unionfs: create opaque directories' whiteouts unconditionally

Needed to maintain Unix semantics (LTP testing).

Signed-off-by: Erez Zadok <ezk@...sunysb.edu>
---
 fs/unionfs/subr.c |   14 ++++++++++++++
 1 files changed, 14 insertions(+), 0 deletions(-)

diff --git a/fs/unionfs/subr.c b/fs/unionfs/subr.c
index 968ee8c..1a26c57 100644
--- a/fs/unionfs/subr.c
+++ b/fs/unionfs/subr.c
@@ -162,6 +162,19 @@ int make_dir_opaque(struct dentry *dentry, int bindex)
 	struct dentry *lower_dentry, *diropq;
 	struct inode *lower_dir;
 	struct nameidata nd;
+	kernel_cap_t orig_cap;
+
+	/*
+	 * Opaque directory whiteout markers are special files (like regular
+	 * whiteouts), and should appear to the users as if they don't
+	 * exist.  They should be created/deleted regardless of directory
+	 * search/create permissions, but only for the duration of this
+	 * creation of the .wh.__dir_opaque: file.  Note, this does not
+	 * circumvent normal ->permission).
+	 */
+	orig_cap = current->cap_effective;
+	cap_raise(current->cap_effective, CAP_DAC_READ_SEARCH);
+	cap_raise(current->cap_effective, CAP_DAC_OVERRIDE);
 
 	lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
 	lower_dir = lower_dentry->d_inode;
@@ -189,6 +202,7 @@ int make_dir_opaque(struct dentry *dentry, int bindex)
 
 out:
 	mutex_unlock(&lower_dir->i_mutex);
+	current->cap_effective = orig_cap;
 	return err;
 }
 
-- 
1.5.2.2

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