From: Casey Schaufler <casey@schaufler-ca.com>
To: Tejun Heo <tj@kernel.org>
Cc: CHANDAN VN <chandan.vn@samsung.com>,
gregkh@linuxfoundation.org, bfields@fieldses.org,
jlayton@kernel.org, linux-kernel@vger.kernel.org,
linux-nfs@vger.kernel.org, cpgs@samsung.com,
sireesha.t@samsung.com, Chris Wright <chrisw@sous-sol.org>,
linux-security-module@vger.kernel.org,
Casey Schaufler <casey@schaufler-ca.com>
Subject: Re: [PATCH 1/1] Fix memory leak in kernfs_security_xattr_set and kernfs_security_xattr_set
Date: Thu, 31 May 2018 09:22:18 -0700 [thread overview]
Message-ID: <1ced6bce-92cc-7e0c-fab4-0aaa3d03b82f@schaufler-ca.com> (raw)
In-Reply-To: <20180531161107.GV1351649@devbig577.frc2.facebook.com>
On 5/31/2018 9:11 AM, Tejun Heo wrote:
> On Thu, May 31, 2018 at 09:04:25AM -0700, Casey Schaufler wrote:
>> On 5/31/2018 8:39 AM, Tejun Heo wrote:
>>> (cc'ing more security folks and copying whole body)
>>>
>>> So, I'm sure the patch fixes the memory leak but API wise it looks
>>> super confusing. Can security folks chime in here? Is this the right
>>> fix?
>> security_inode_getsecctx() provides a security context. Technically,
>> this is a data blob, although both provider provide a null terminated
>> string. security_inode_getsecurity(), on the other hand, provides a
>> string to match an attribute name. The former releases the security
>> context with security_release_secctx(), where the later releases the
>> string with kfree().
>>
>> When the Smack hook smack_inode_getsecctx() was added in 2009
>> for use by labeled NFS the alloc value passed to
>> smack_inode_getsecurity() was set incorrectly. This wasn't a
>> major issue, since labeled NFS is a fringe case. When kernfs
>> started using the hook, it became the issue you discovered.
>>
>> The reason that we have all this confusion is that SELinux
>> generates security contexts as needed, while Smack keeps them
>> around all the time. Releasing an SELinux context frees memory,
>> while releasing a Smack context is a null operation.
> Any chance this detail can be hidden behind security api? This looks
> pretty error-prone, no?
It *is* hidden behind the security API. The problem is strictly
within the Smack code, where the implementer of smack_inode_getsecctx()
made an error.
>
> Thanks.
>
next prev parent reply other threads:[~2018-05-31 16:22 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20180531092848epcas1p24b638ccd6da00f1e039bdb64de7e1a5b@epcas1p2.samsung.com>
2018-05-31 9:28 ` [PATCH 1/1] Fix memory leak in kernfs_security_xattr_set and kernfs_security_xattr_set CHANDAN VN
2018-05-31 15:26 ` Casey Schaufler
2018-05-31 20:57 ` Eric W. Biederman
2018-05-31 21:08 ` Casey Schaufler
2018-05-31 15:39 ` Tejun Heo
2018-05-31 16:04 ` Casey Schaufler
2018-05-31 16:11 ` Tejun Heo
2018-05-31 16:22 ` Casey Schaufler [this message]
[not found] ` <CGME20180531092848epcas1p24b638ccd6da00f1e039bdb64de7e1a5b@epcms5p5>
2018-06-01 8:56 ` CHANDAN VN
2018-06-01 16:22 ` Casey Schaufler
[not found] ` <CGME20180531092848epcas1p24b638ccd6da00f1e039bdb64de7e1a5b@epcms5p7>
2018-06-01 16:29 ` CHANDAN VN
2018-06-01 16:41 ` Casey Schaufler
2018-06-01 17:45 ` [PATCH] Smack: Fix memory leak in smack_inode_getsecctx Casey Schaufler
2018-06-04 21:01 ` Casey Schaufler
2018-06-04 21:27 ` Tejun Heo
[not found] ` <CGME20180531092848epcas1p24b638ccd6da00f1e039bdb64de7e1a5b@epcms5p3>
2018-06-05 7:04 ` CHANDAN VN
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1ced6bce-92cc-7e0c-fab4-0aaa3d03b82f@schaufler-ca.com \
--to=casey@schaufler-ca.com \
--cc=bfields@fieldses.org \
--cc=chandan.vn@samsung.com \
--cc=chrisw@sous-sol.org \
--cc=cpgs@samsung.com \
--cc=gregkh@linuxfoundation.org \
--cc=jlayton@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-nfs@vger.kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=sireesha.t@samsung.com \
--cc=tj@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).