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From: THOBY Simon <Simon.THOBY@viveris.fr>
To: Mimi Zohar <zohar@linux.ibm.com>,
	"dmitry.kasatkin@gmail.com" <dmitry.kasatkin@gmail.com>,
	"linux-integrity@vger.kernel.org"
	<linux-integrity@vger.kernel.org>,
	BARVAUX Didier <Didier.BARVAUX@viveris.fr>
Cc: Paul Moore <paul@paul-moore.com>
Subject: Re: [PATCH v4 2/5] IMA: block writes of the security.ima xattr with unsupported algorithms
Date: Wed, 28 Jul 2021 07:00:18 +0000	[thread overview]
Message-ID: <529bc35e-642f-9f50-f3a7-0d3c07890afe@viveris.fr> (raw)
In-Reply-To: <5a3a35b5f20fb17f7430046b0378e05f1dffa098.camel@linux.ibm.com>

Hi Mimi,

On 7/27/21 10:32 PM, Mimi Zohar wrote:
> [Cc'ing Paul Moore]
> 
> Hi Simon,
> 

[snip]

> 
>> +
>> +	if (likely(dentry_hash == ima_hash_algo
>> +	    || crypto_has_alg(hash_algo_name[dentry_hash], 0, 0)))
>> +		return 0;
>> +
>> +	pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
>> +	/* no memory available ? no file path for you */
> 
> The comment here is unnecessary.  Avoid or limit comments inside a
> function.  Refer to the section "8) Commenting" in
> Documentation/process/coding-style.rst
> 
>> +	if (pathbuf)
>> +		path = dentry_path(dentry, pathbuf, PATH_MAX);
>> +
>> +	/* disallow xattr writes with algorithms not built in the kernel */
>> +	integrity_audit_msg(AUDIT_INTEGRITY_DATA, d_inode(dentry),
>> +		path, "collect_data", "unavailable-hash-algorithm", res, 0);
> 
> This will emit an audit message without the filename when !path.  Is
> this what you intended?
> 

This is what I was clumsily trying to explain in the previous comment: if we cannot
allocate memory for a file path, I thought it best to log the audit message without
the path than fail with a -ENOMEM (auditing will also try to allocate a memory buffer
too, but a bit smaller, and memory could have been reclaimed between the two calls,
so the auditing operation may succeed).

Of course I could also return -ENOMEM, and it would happily propagate back to the user.

What do you think ?

Thanks,
Simon

  reply	other threads:[~2021-07-28  7:00 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-27 16:33 [PATCH v4 0/5] IMA: restrict the accepted digest algorithms for THOBY Simon
2021-07-27 16:33 ` [PATCH v4 1/5] IMA: remove the dependency on CRYPTO_MD5 THOBY Simon
2021-07-27 17:57   ` Mimi Zohar
2021-07-27 16:33 ` [PATCH v4 2/5] IMA: block writes of the security.ima xattr with unsupported algorithms THOBY Simon
2021-07-27 20:32   ` Mimi Zohar
2021-07-28  7:00     ` THOBY Simon [this message]
2021-07-28 12:43       ` Mimi Zohar
2021-07-28 12:53         ` THOBY Simon
2021-07-28 13:09           ` Mimi Zohar
2021-07-27 16:33 ` [PATCH v4 3/5] IMA: add support to restrict the hash algorithms used for file appraisal THOBY Simon
2021-07-27 20:38   ` Mimi Zohar
2021-07-27 16:33 ` [PATCH v4 4/5] IMA: add a policy option to restrict xattr hash algorithms on appraisal THOBY Simon
2021-07-27 21:07   ` Mimi Zohar
2021-07-27 16:33 ` [PATCH v4 5/5] IMA: introduce a new policy option func=SETXATTR_CHECK THOBY Simon
2021-07-27 17:25   ` Mimi Zohar
2021-07-27 17:58     ` THOBY Simon
2021-07-27 17:47 ` [PATCH v4 0/5] IMA: restrict the accepted digest algorithms for Mimi Zohar

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