linux-kernel - [PATCH 25/32] Unionfs: readonly branch test fix

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Message-Id: <118878605894-git-send-email-jsipek@cs.sunysb.edu>
Date:	Sun,  2 Sep 2007 22:20:48 -0400
From:	"Josef 'Jeff' Sipek" <jsipek@...sunysb.edu>
To:	akpm@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	hch@...radead.org, viro@....linux.org.uk,
	bharata@...ux.vnet.ibm.com, j.blunck@...harburg.de,
	Erez Zadok <ezk@...sunysb.edu>,
	"Josef 'Jeff' Sipek" <jsipek@...sunysb.edu>
Subject: [PATCH 25/32] Unionfs: readonly branch test fix

From: Erez Zadok <ezk@...sunysb.edu>

Bug fix to test if a lower branch is readonly, even when given negative
dentries.

Signed-off-by: Erez Zadok <ezk@...sunysb.edu>
Signed-off-by: Josef 'Jeff' Sipek <jsipek@...sunysb.edu>
---
 fs/unionfs/union.h |   19 ++++++++++++++-----
 1 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/fs/unionfs/union.h b/fs/unionfs/union.h
index 33c2137..26d886e 100644
--- a/fs/unionfs/union.h
+++ b/fs/unionfs/union.h
@@ -396,14 +396,23 @@ static inline int is_robranch_super(const struct super_block *sb, int index)
 /* Is this file on a read-only branch? */
 static inline int is_robranch_idx(const struct dentry *dentry, int index)
 {
-	int err = 0;
+	struct super_block *lower_sb;
 
 	BUG_ON(index < 0);
 
-	if ((!(branchperms(dentry->d_sb, index) & MAY_WRITE)) ||
-	    IS_RDONLY(unionfs_lower_dentry_idx(dentry, index)->d_inode))
-		err = -EROFS;
-	return err;
+	if (!(branchperms(dentry->d_sb, index) & MAY_WRITE))
+		return -EROFS;
+
+	lower_sb = unionfs_lower_super_idx(dentry->d_sb, index);
+	BUG_ON(lower_sb == NULL);
+	/*
+	 * test sb flags directly, not IS_RDONLY(lower_inode) because the
+	 * lower_dentry could be a negative.
+	 */
+	if (lower_sb->s_flags & MS_RDONLY)
+		return -EROFS;
+
+	return 0;
 }
 
 static inline int is_robranch(const struct dentry *dentry)
-- 
1.5.2.2.238.g7cbf2f2

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