linux-kernel - [ 40/82] vfs: increment iversion when a file is truncated

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Message-Id: <20120608041846.208742839@decadent.org.uk>
Date:	Fri, 08 Jun 2012 05:19:20 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk,
	Dmitry Kasatkin <dmitry.kasatkin@...el.com>,
	Mimi Zohar <zohar@...ibm.com>,
	Al Viro <viro@...iv.linux.org.uk>
Subject: [ 40/82] vfs: increment iversion when a file is truncated

3.2-stable review patch.  If anyone has any objections, please let me know.

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

From: Dmitry Kasatkin <dmitry.kasatkin@...el.com>

commit 799243a389bde0de10fa21ca1ca453d2fe538b85 upstream.

When a file is truncated with truncate()/ftruncate() and then closed,
iversion is not updated.  This patch uses ATTR_SIZE flag as an indication
to increment iversion.

Mimi said:

On fput(), i_version is used to detect and flag files that have changed
and need to be re-measured in the IMA measurement policy.  When a file
is truncated with truncate()/ftruncate() and then closed, i_version is
not updated.  As a result, although the file has changed, it will not be
re-measured and added to the IMA measurement list on subsequent access.

Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@...el.com>
Acked-by: Mimi Zohar <zohar@...ibm.com>
Cc: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/attr.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/fs/attr.c
+++ b/fs/attr.c
@@ -176,6 +176,11 @@
 			return -EPERM;
 	}
 
+	if ((ia_valid & ATTR_SIZE) && IS_I_VERSION(inode)) {
+		if (attr->ia_size != inode->i_size)
+			inode_inc_iversion(inode);
+	}
+
 	if ((ia_valid & ATTR_MODE)) {
 		mode_t amode = attr->ia_mode;
 		/* Flag setting protected by i_mutex */


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