linux-kernel - [PATCH 3.2 047/107] eCryptfs: Invalidate dcache entries when lower i

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Message-ID: <lsq.1444349548.815492944@decadent.org.uk>
Date:	Fri, 09 Oct 2015 01:12:28 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Richard Weinberger" <richard@....at>,
	"Tyler Hicks" <tyhicks@...onical.com>
Subject: [PATCH 3.2 047/107] eCryptfs: Invalidate dcache entries when
 lower i_nlink is zero

3.2.72-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Tyler Hicks <tyhicks@...onical.com>

commit 5556e7e6d30e8e9b5ee51b0e5edd526ee80e5e36 upstream.

Consider eCryptfs dcache entries to be stale when the corresponding
lower inode's i_nlink count is zero. This solves a problem caused by the
lower inode being directly modified, without going through the eCryptfs
mount, leaving stale eCryptfs dentries cached and the eCryptfs inode's
i_nlink count not being cleared.

Signed-off-by: Tyler Hicks <tyhicks@...onical.com>
Reported-by: Richard Weinberger <richard@....at>
[bwh: Backported to 3.2:
 - Test d_revalidate pointer directly rather than a DCACHE_OP flag
 - Open-code d_inode()
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/ecryptfs/dentry.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

--- a/fs/ecryptfs/dentry.c
+++ b/fs/ecryptfs/dentry.c
@@ -55,26 +55,26 @@ static int ecryptfs_d_revalidate(struct
 
 	lower_dentry = ecryptfs_dentry_to_lower(dentry);
 	lower_mnt = ecryptfs_dentry_to_lower_mnt(dentry);
-	if (!lower_dentry->d_op || !lower_dentry->d_op->d_revalidate)
-		goto out;
-	if (nd) {
-		dentry_save = nd->path.dentry;
-		vfsmount_save = nd->path.mnt;
-		nd->path.dentry = lower_dentry;
-		nd->path.mnt = lower_mnt;
-	}
-	rc = lower_dentry->d_op->d_revalidate(lower_dentry, nd);
-	if (nd) {
-		nd->path.dentry = dentry_save;
-		nd->path.mnt = vfsmount_save;
+	if (lower_dentry->d_op && lower_dentry->d_op->d_revalidate) {
+		if (nd) {
+			dentry_save = nd->path.dentry;
+			vfsmount_save = nd->path.mnt;
+			nd->path.dentry = lower_dentry;
+			nd->path.mnt = lower_mnt;
+		}
+		rc = lower_dentry->d_op->d_revalidate(lower_dentry, nd);
+		if (nd) {
+			nd->path.dentry = dentry_save;
+			nd->path.mnt = vfsmount_save;
+		}
 	}
 	if (dentry->d_inode) {
-		struct inode *lower_inode =
-			ecryptfs_inode_to_lower(dentry->d_inode);
+		struct inode *inode = dentry->d_inode;
 
-		fsstack_copy_attr_all(dentry->d_inode, lower_inode);
+		fsstack_copy_attr_all(inode, ecryptfs_inode_to_lower(inode));
+		if (!inode->i_nlink)
+			return 0;
 	}
-out:
 	return rc;
 }
 

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