From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from out03.mta.xmission.com ([166.70.13.233]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1fDt4c-0008F5-Vi for kexec@lists.infradead.org; Wed, 02 May 2018 14:49:40 +0000 From: ebiederm@xmission.com (Eric W. Biederman) References: <1523572911-16363-1-git-send-email-zohar@linux.vnet.ibm.com> <1523572911-16363-3-git-send-email-zohar@linux.vnet.ibm.com> Date: Wed, 02 May 2018 09:45:30 -0500 In-Reply-To: <1523572911-16363-3-git-send-email-zohar@linux.vnet.ibm.com> (Mimi Zohar's message of "Thu, 12 Apr 2018 18:41:50 -0400") Message-ID: <87h8nqglpx.fsf@xmission.com> MIME-Version: 1.0 Subject: Re: [PATCH 2/3] kexec: call LSM hook for kexec_load syscall List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Mimi Zohar Cc: kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Matthew Garrett , David Howells , linux-security-module@vger.kernel.org, linux-integrity@vger.kernel.org Mimi Zohar writes: > Allow LSMs and IMA to differentiate between the kexec_load and > kexec_file_load syscalls by adding an "unnecessary" call to > security_kernel_read_file() in kexec_load. This would be similar to the > existing init_module syscall calling security_kernel_read_file(). Given the reasonable desire to load a policy that ensures everything has a signature I don't have fundamental objections. security_kernel_read_file as a hook seems an odd choice. At the very least it has a bad name because there is no file reading going on here. I am concerned that I don't see CONFIG_KEXEC_VERIFY_SIG being tested anywhere. Which means I could have a kernel compiled without that and I would be allowed to use kexec_file_load without signature checking. While kexec_load would be denied. Am I missing something here? Eric > Signed-off-by: Mimi Zohar > --- > kernel/kexec.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/kernel/kexec.c b/kernel/kexec.c > index aed8fb2564b3..d1386cfc6796 100644 > --- a/kernel/kexec.c > +++ b/kernel/kexec.c > @@ -11,6 +11,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -195,11 +196,21 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments, > static inline int kexec_load_check(unsigned long nr_segments, > unsigned long flags) > { > + int result; > + > /* We only trust the superuser with rebooting the system. */ > if (!capable(CAP_SYS_BOOT) || kexec_load_disabled) > return -EPERM; > > /* > + * Allow LSMs and IMA to differentiate between kexec_load and > + * kexec_file_load syscalls. > + */ > + result = security_kernel_read_file(NULL, READING_KEXEC_IMAGE); > + if (result < 0) > + return result; > + > + /* > * Verify we have a legal set of flags > * This leaves us room for future extensions. > */ _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from out03.mta.xmission.com ([166.70.13.233]:53450 "EHLO out03.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751652AbeEBOt1 (ORCPT ); Wed, 2 May 2018 10:49:27 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: Mimi Zohar Cc: David Howells , Matthew Garrett , linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org References: <1523572911-16363-1-git-send-email-zohar@linux.vnet.ibm.com> <1523572911-16363-3-git-send-email-zohar@linux.vnet.ibm.com> Date: Wed, 02 May 2018 09:45:30 -0500 In-Reply-To: <1523572911-16363-3-git-send-email-zohar@linux.vnet.ibm.com> (Mimi Zohar's message of "Thu, 12 Apr 2018 18:41:50 -0400") Message-ID: <87h8nqglpx.fsf@xmission.com> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [PATCH 2/3] kexec: call LSM hook for kexec_load syscall Sender: linux-integrity-owner@vger.kernel.org List-ID: Mimi Zohar writes: > Allow LSMs and IMA to differentiate between the kexec_load and > kexec_file_load syscalls by adding an "unnecessary" call to > security_kernel_read_file() in kexec_load. This would be similar to the > existing init_module syscall calling security_kernel_read_file(). Given the reasonable desire to load a policy that ensures everything has a signature I don't have fundamental objections. security_kernel_read_file as a hook seems an odd choice. At the very least it has a bad name because there is no file reading going on here. I am concerned that I don't see CONFIG_KEXEC_VERIFY_SIG being tested anywhere. Which means I could have a kernel compiled without that and I would be allowed to use kexec_file_load without signature checking. While kexec_load would be denied. Am I missing something here? Eric > Signed-off-by: Mimi Zohar > --- > kernel/kexec.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/kernel/kexec.c b/kernel/kexec.c > index aed8fb2564b3..d1386cfc6796 100644 > --- a/kernel/kexec.c > +++ b/kernel/kexec.c > @@ -11,6 +11,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -195,11 +196,21 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments, > static inline int kexec_load_check(unsigned long nr_segments, > unsigned long flags) > { > + int result; > + > /* We only trust the superuser with rebooting the system. */ > if (!capable(CAP_SYS_BOOT) || kexec_load_disabled) > return -EPERM; > > /* > + * Allow LSMs and IMA to differentiate between kexec_load and > + * kexec_file_load syscalls. > + */ > + result = security_kernel_read_file(NULL, READING_KEXEC_IMAGE); > + if (result < 0) > + return result; > + > + /* > * Verify we have a legal set of flags > * This leaves us room for future extensions. > */ From mboxrd@z Thu Jan 1 00:00:00 1970 From: ebiederm@xmission.com (Eric W. Biederman) Date: Wed, 02 May 2018 09:45:30 -0500 Subject: [PATCH 2/3] kexec: call LSM hook for kexec_load syscall In-Reply-To: <1523572911-16363-3-git-send-email-zohar@linux.vnet.ibm.com> (Mimi Zohar's message of "Thu, 12 Apr 2018 18:41:50 -0400") References: <1523572911-16363-1-git-send-email-zohar@linux.vnet.ibm.com> <1523572911-16363-3-git-send-email-zohar@linux.vnet.ibm.com> Message-ID: <87h8nqglpx.fsf@xmission.com> To: linux-security-module@vger.kernel.org List-Id: linux-security-module.vger.kernel.org Mimi Zohar writes: > Allow LSMs and IMA to differentiate between the kexec_load and > kexec_file_load syscalls by adding an "unnecessary" call to > security_kernel_read_file() in kexec_load. This would be similar to the > existing init_module syscall calling security_kernel_read_file(). Given the reasonable desire to load a policy that ensures everything has a signature I don't have fundamental objections. security_kernel_read_file as a hook seems an odd choice. At the very least it has a bad name because there is no file reading going on here. I am concerned that I don't see CONFIG_KEXEC_VERIFY_SIG being tested anywhere. Which means I could have a kernel compiled without that and I would be allowed to use kexec_file_load without signature checking. While kexec_load would be denied. Am I missing something here? Eric > Signed-off-by: Mimi Zohar > --- > kernel/kexec.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/kernel/kexec.c b/kernel/kexec.c > index aed8fb2564b3..d1386cfc6796 100644 > --- a/kernel/kexec.c > +++ b/kernel/kexec.c > @@ -11,6 +11,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -195,11 +196,21 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments, > static inline int kexec_load_check(unsigned long nr_segments, > unsigned long flags) > { > + int result; > + > /* We only trust the superuser with rebooting the system. */ > if (!capable(CAP_SYS_BOOT) || kexec_load_disabled) > return -EPERM; > > /* > + * Allow LSMs and IMA to differentiate between kexec_load and > + * kexec_file_load syscalls. > + */ > + result = security_kernel_read_file(NULL, READING_KEXEC_IMAGE); > + if (result < 0) > + return result; > + > + /* > * Verify we have a legal set of flags > * This leaves us room for future extensions. > */ -- To unsubscribe from this list: send the line "unsubscribe linux-security-module" in the body of a message to majordomo at vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html