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Biederman" , David Howells Cc: torvalds@linux-foundation.org, linux-man@vger.kernel.org, linux-api@vger.kernel.org, jmorris@namei.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org Date: Wed, 11 Apr 2018 16:09:35 -0400 In-Reply-To: <87po35k1q6.fsf@xmission.com> References: <152346387861.4030.4408662483445703127.stgit@warthog.procyon.org.uk> <152346391877.4030.6270466586590461223.stgit@warthog.procyon.org.uk> <87po35k1q6.fsf@xmission.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.20.5 (3.20.5-1.fc24) Mime-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 18041120-0012-0000-0000-000005C9BD7D X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18041120-0013-0000-0000-00001945EF8C Message-Id: <1523477375.5268.78.camel@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-04-11_09:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=3 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1804110186 Sender: linux-api-owner@vger.kernel.org X-Mailing-List: linux-api@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Wed, 2018-04-11 at 14:00 -0500, Eric W. Biederman wrote: > David Howells writes: > > > From: Matthew Garrett > > > > The kexec_load() syscall permits the loading and execution of arbitrary > > code in ring 0, which is something that lock-down is meant to prevent. It > > makes sense to disable kexec_load() in this situation. > > > > This does not affect kexec_file_load() syscall which can check for a > > signature on the image to be booted. > > Maybing I am missing it but I am not seeing anything that would require > kexec_file_load be configured such that it checks the loaded kernel. > > Without that I don't see the point of disabling kexec_load. > > Nacked-by: "Eric W. Biederman" The IMA "secure boot" policy requires the kexec image to be signed.  This call to kernel_is_locked_down() could be replaced with a call to security_kernel_read_file(NULL, READING_KEXEC_IMAGE). It would be similar to the existing init_module syscall calling security_kernel_read_file(). Mimi