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

[Ben Hutchings]

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

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

From: Dmitry Kasatkin <dmitry.kasatkin@xxxxxxxxx>

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@xxxxxxxxx>
Acked-by: Mimi Zohar <zohar@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 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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