linux-kernel - Re: [PATCH 1/1] Fix memory leak in kernfs_security_xattr_set and kernfs_security_xattr

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Date:   Fri, 1 Jun 2018 09:41:39 -0700
From:   Casey Schaufler <casey@...aufler-ca.com>
To:     chandan.vn@...sung.com,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>
Cc:     Tejun Heo <tj@...nel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "bfields@...ldses.org" <bfields@...ldses.org>,
        "jlayton@...nel.org" <jlayton@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
        CPGS <cpgs@...sung.com>,
        Sireesha Talluri <sireesha.t@...sung.com>,
        Chris Wright <chrisw@...s-sol.org>,
        Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [PATCH 1/1] Fix memory leak in kernfs_security_xattr_set and
 kernfs_security_xattr_set

On 6/1/2018 9:29 AM, CHANDAN VN wrote:
>>>  I agree that the fix can be done simply by using "false" for 
>>>  smack_inode_getsecurity(), but what happens with kernfs_node_setsecdata()
>>>  and smack_inode_notifysecctx(). kernfs_node_setsecdata() is probably ignorable
>>>  but smack_inode_notifysecctx() is sending the "ctx" to smack_inode_setsecurity()
>>>  and since "ctx" would be NULL because we used "false", smack_inode_setsecurity()
>>>  becomes dummy.
>  
>> Thank you for pointing this out. You're right, there's more
>> at issue here than changing the alloc flag will fix. I think
>> that calling smack_inode_getsecurity() from smack_inode_getsecctx()
>> is making the code more complicated than it needs to be. I will
>> have a patch shortly.
> If you think the patch would take time or is complicated, I suggest that the kfree() fix should go
> to fix the leaks for now.

Heavens no! The patch is very simple. I'm building a kernel with
it now, and should have it tested and posted within a few hours.
The implementation of smack_inode_getsecctx() that's there is
understandable, but wrong. There's a much better way to do the
job.