Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH net-next] modules: allow modprobe load regular elf
 binaries
To:     Randy Dunlap <rdunlap@infradead.org>,
        Alexei Starovoitov <ast@kernel.org>, <davem@davemloft.net>
References: <20180306013457.1955486-1-ast@kernel.org>
 <67abc3a2-80c9-7223-37c2-e15bbecdcd00@infradead.org>
CC:     <daniel@iogearbox.net>, <torvalds@linux-foundation.org>,
        <gregkh@linuxfoundation.org>, <mcgrof@kernel.org>,
        <netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <kernel-team@fb.com>, <linux-api@vger.kernel.org>
From:   Alexei Starovoitov <ast@fb.com>
Message-ID: <eaaac6df-6deb-46e7-3020-83a97221d1f8@fb.com>
Date:   Mon, 5 Mar 2018 19:02:12 -0800
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:45.0)
 Gecko/20100101 Thunderbird/45.8.0
MIME-Version: 1.0
In-Reply-To: <67abc3a2-80c9-7223-37c2-e15bbecdcd00@infradead.org>
Content-Type: text/plain; charset="utf-8"; format=flowed
Content-Transfer-Encoding: 7bit
Received-SPF: None (protection.outlook.com: fb.com does not designate
 permitted sender hosts)
SpamDiagnosticOutput: 1:99
SpamDiagnosticMetadata: NSPM
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Mar 2018 03:02:17.0847 (UTC)
X-MS-Exchange-CrossTenant-Network-Message-Id: 74bd899c-0e81-4864-af82-08d5830eac62
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB2504
X-OriginatorOrg: fb.com
X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2018-03-06_01:,,
 signatures=0
X-Proofpoint-Spam-Reason: safe
X-FB-Internal: Safe
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 3/5/18 6:13 PM, Randy Dunlap wrote:
> Hi,
>
> On 03/05/2018 05:34 PM, Alexei Starovoitov wrote:
>
>> diff --git a/kernel/module.c b/kernel/module.c
>> index ad2d420024f6..6cfa35795741 100644
>> --- a/kernel/module.c
>> +++ b/kernel/module.c
>
>> @@ -3669,6 +3683,17 @@ static int load_module(struct load_info *info, const char __user *uargs,
>>  	if (err)
>>  		goto free_copy;
>>
>> +	if (info->hdr->e_type == ET_EXEC) {
>> +#ifdef CONFIG_MODULE_SIG
>> +		if (!info->sig_ok) {
>> +			pr_notice_once("umh %s verification failed: signature and/or required key missing - tainting kernel\n",
>
> That's not a very friendly message to tell a user.  "umh" eh?

umh is an abbreviation known to kernel newbies:
https://kernelnewbies.org/KernelProjects/usermode-helper-enhancements

The rest of the message is copy paste of existing one.

>> +				       info->file->f_path.dentry->d_name.name);
>> +			add_taint(TAINT_UNSIGNED_MODULE, LOCKDEP_STILL_OK);
>> +		}
>
> And since the signature failed, why is it being loaded at all?

because this is how regular kernel modules deal with it.
sig_enforce is handled earlier.

> Is this in the "--force" load path?

--force forces modver and modmagic. These things don't apply here.