linux-kernel - [PATCH 1/3] ima: verify mprotect change is consistent with mmap policy

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Message-Id: <1557161824-6623-2-git-send-email-zohar@linux.ibm.com>
Date:   Mon,  6 May 2019 12:57:02 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     linux-integrity@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Igor Zhbanov <i.zhbanov@...russia.ru>,
        Jordan Glover <Golden_Miller83@...tonmail.ch>,
        Al Viro <viro@...iv.linux.org.uk>,
        Mimi Zohar <zohar@...ux.ibm.com>
Subject: [PATCH 1/3] ima: verify mprotect change is consistent with mmap policy

IMA can be configured to measure and appraise a file's integrity being
mmap'ed execute.  Files can be mmap'ed read/write and later changed to
execute to circumvent IMA's mmap measurement and appraisal policy rules.

To prevent this from happening, this patch similarly calls
ima_file_mmap() for mprotect changes.

Suggested-by: Stephen Smalley <sds@...ho.nsa.gov>
Signed-off-by: Mimi Zohar <zohar@...ux.ibm.com>
---
 security/security.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/security/security.c b/security/security.c
index 23cbb1a295a3..98ce27933e72 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1411,7 +1411,12 @@ int security_mmap_addr(unsigned long addr)
 int security_file_mprotect(struct vm_area_struct *vma, unsigned long reqprot,
 			    unsigned long prot)
 {
-	return call_int_hook(file_mprotect, 0, vma, reqprot, prot);
+	int ret;
+
+	ret = call_int_hook(file_mprotect, 0, vma, reqprot, prot);
+	if (ret)
+		return ret;
+	return ima_file_mmap(vma->vm_file, prot);
 }
 
 int security_file_lock(struct file *file, unsigned int cmd)
-- 
2.7.5