linux-kernel - [PATCH] ima: fix off-by-one comparison on template name length

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Date:   Tue, 20 Sep 2016 18:25:27 +0100
From:   Colin King <colin.king@...onical.com>
To:     Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        James Morris <james.l.morris@...cle.com>,
        "Serge E . Hallyn" <serge@...lyn.com>,
        linux-ima-devel@...ts.sourceforge.net,
        linux-ima-user@...ts.sourceforge.net,
        linux-security-module@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH] ima: fix off-by-one comparison on template name length

From: Colin Ian King <colin.king@...onical.com>

The comparison of dr_v1->template_name_len is off-by-one, so
currently if the length is MAX_TEMPLATE_NAME_LEN we end up
with an out-of-bounds write on template_name when the terminating
zero character is written. Fix the comparison.

Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 security/integrity/ima/ima_template.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/security/integrity/ima/ima_template.c b/security/integrity/ima/ima_template.c
index 24775f3..004723c 100644
--- a/security/integrity/ima/ima_template.c
+++ b/security/integrity/ima/ima_template.c
@@ -395,7 +395,7 @@ int ima_restore_measurement_list(loff_t size, void *buf)
 			hdr_v1->template_name_len =
 			    le32_to_cpu(hdr_v1->template_name_len);
 
-		if ((hdr_v1->template_name_len > MAX_TEMPLATE_NAME_LEN) ||
+		if ((hdr_v1->template_name_len >= MAX_TEMPLATE_NAME_LEN) ||
 		    ((bufp + hdr_v1->template_name_len) > bufendp)) {
 			pr_err("attempting to restore a template name \
 				that is too long\n");
-- 
2.9.3