linux-kernel - [PATCH 0/1] ima: check control characters in policy path

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Date:   Sat, 14 Aug 2021 16:13:55 +0800
From:   Tianxing Zhang <anakinzhang96@...il.com>
To:     zohar@...ux.ibm.com
Cc:     linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Tianxing Zhang <anakinzhang96@...il.com>
Subject: [PATCH 0/1] ima: check control characters in policy path

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