From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-vs1-xe4a.google.com ([2607:f8b0:4864:20::e4a]) by bombadil.infradead.org with esmtps (Exim 4.92 #3 (Red Hat Linux)) id 1heTVz-00024Q-Pb for kexec@lists.infradead.org; Sat, 22 Jun 2019 00:04:21 +0000 Received: by mail-vs1-xe4a.google.com with SMTP id 129so2858797vsx.13 for ; Fri, 21 Jun 2019 17:04:17 -0700 (PDT) Date: Fri, 21 Jun 2019 17:03:35 -0700 In-Reply-To: <20190622000358.19895-1-matthewgarrett@google.com> Message-Id: <20190622000358.19895-7-matthewgarrett@google.com> Mime-Version: 1.0 References: <20190622000358.19895-1-matthewgarrett@google.com> Subject: [PATCH V34 06/29] kexec_load: Disable at runtime if the kernel is locked down From: Matthew Garrett 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: jmorris@namei.org Cc: Matthew Garrett , linux-api@vger.kernel.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Matthew Garrett , David Howells , linux-security-module@vger.kernel.org, Dave Young 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. Signed-off-by: David Howells Signed-off-by: Matthew Garrett Acked-by: Dave Young cc: kexec@lists.infradead.org --- include/linux/security.h | 1 + kernel/kexec.c | 8 ++++++++ security/lockdown/lockdown.c | 1 + 3 files changed, 10 insertions(+) diff --git a/include/linux/security.h b/include/linux/security.h index 200175c8605a..00a31ab2e5ba 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -84,6 +84,7 @@ enum lockdown_reason { LOCKDOWN_NONE, LOCKDOWN_MODULE_SIGNATURE, LOCKDOWN_DEV_MEM, + LOCKDOWN_KEXEC, LOCKDOWN_INTEGRITY_MAX, LOCKDOWN_CONFIDENTIALITY_MAX, }; diff --git a/kernel/kexec.c b/kernel/kexec.c index 68559808fdfa..ec3f07a4b1c0 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -207,6 +207,14 @@ static inline int kexec_load_check(unsigned long nr_segments, if (result < 0) return result; + /* + * kexec can be used to circumvent module loading restrictions, so + * prevent loading in that case + */ + result = security_locked_down(LOCKDOWN_KEXEC); + if (result) + return result; + /* * Verify we have a legal set of flags * This leaves us room for future extensions. diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c index 565c87451f0f..08fcd8116db3 100644 --- a/security/lockdown/lockdown.c +++ b/security/lockdown/lockdown.c @@ -20,6 +20,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = { [LOCKDOWN_NONE] = "none", [LOCKDOWN_MODULE_SIGNATURE] = "unsigned module loading", [LOCKDOWN_DEV_MEM] = "/dev/mem,kmem,port", + [LOCKDOWN_KEXEC] = "kexec of unsigned images", [LOCKDOWN_INTEGRITY_MAX] = "integrity", [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", }; -- 2.22.0.410.gd8fdbe21b5-goog _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec