linux-kernel - [PATCH 3.16 005/134] ima: accept previously set IMA_NEW

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Date:   Fri, 18 Aug 2017 14:13:20 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Daniel Glöckner" <dg@...ix.com>,
        "Mimi Zohar" <zohar@...ux.vnet.ibm.com>
Subject: [PATCH 3.16 005/134] ima: accept previously set IMA_NEW_FILE

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

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

From: Daniel Glöckner <dg@...ix.com>

commit 1ac202e978e18f045006d75bd549612620c6ec3a upstream.

Modifying the attributes of a file makes ima_inode_post_setattr reset
the IMA cache flags. So if the file, which has just been created,
is opened a second time before the first file descriptor is closed,
verification fails since the security.ima xattr has not been written
yet. We therefore have to look at the IMA_NEW_FILE even if the file
already existed.

With this patch there should no longer be an error when cat tries to
open testfile:

$ rm -f testfile
$ ( echo test >&3 ; touch testfile ; cat testfile ) 3>testfile

A file being new is no reason to accept that it is missing a digital
signature demanded by the policy.

Signed-off-by: Daniel Glöckner <dg@...ix.com>
Signed-off-by: Mimi Zohar <zohar@...ux.vnet.ibm.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 security/integrity/ima/ima_appraise.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -195,10 +195,11 @@ int ima_appraise_measurement(int func, s

 		cause = "missing-hash";
 		status = INTEGRITY_NOLABEL;
-		if (opened & FILE_CREATED) {
+		if (opened & FILE_CREATED)
 			iint->flags |= IMA_NEW_FILE;
+		if ((iint->flags & IMA_NEW_FILE) &&
+		    !(iint->flags & IMA_DIGSIG_REQUIRED))
 			status = INTEGRITY_PASS;
-		}
 		goto out;
 	}