Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Tianxing Zhang <anakinzhang96@gmail.com>
To:     zohar@linux.ibm.com
Cc:     linux-integrity@vger.kernel.org,
        linux-security-module@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Tianxing Zhang <anakinzhang96@gmail.com>
Subject: [PATCH 0/1] ima: check control characters in policy path
Date:   Sat, 14 Aug 2021 16:13:55 +0800
Message-Id: <20210814081356.293-1-anakinzhang96@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Hi,

IMA policy can be updated with /sys/kernel/security/ima/policy interface when
CONFIG_IMA_WRITE_POLICY is set. However, kernel does not check the file path
carefully. It only checks if the path has '/' prefix.

When a policy file path contains control characters like '\r' or '\b',
invalid error messages can be printed to overwrite system messages.

For example:

$ echo -e "/\rtest invalid path: ddddddddddddddddddddd" > /sys/kernel/security/ima/policy
$ dmesg
test invalid path: ddddddddddddddddddddd (-2) 

After adding this patch, we'll be able to throw out error message:

$ echo -e "/\rtest invalid path: ddddddddddddddddddddd" > /sys/kernel/security/ima/policy
-bash: echo: write error: Invalid argument
$ dmesg
[   11.684004] ima: invalid path (control characters are not allowed)
[   11.684071] ima: policy update failed

Any suggestions would be appreciated, thank you.

Tianxing Zhang (1):
  ima: check control characters in policy file path

 security/integrity/ima/ima_fs.c | 9 +++++++++
 1 file changed, 9 insertions(+)

-- 
2.25.1