From nobody Mon Apr 13 14:29:33 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5F2E5C4332F for ; Mon, 14 Nov 2022 13:19:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237476AbiKNNT4 (ORCPT ); Mon, 14 Nov 2022 08:19:56 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46148 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237592AbiKNNTf (ORCPT ); Mon, 14 Nov 2022 08:19:35 -0500 Received: from mail-ej1-x633.google.com (mail-ej1-x633.google.com [IPv6:2a00:1450:4864:20::633]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A14802BB18 for ; Mon, 14 Nov 2022 05:19:07 -0800 (PST) Received: by mail-ej1-x633.google.com with SMTP id t25so28189747ejb.8 for ; Mon, 14 Nov 2022 05:19:07 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:subject:date:from:from:to:cc:subject:date:message-id :reply-to; bh=xM+YcVXCVdAbnW4OE/73urNUlHdnFwO79q+gmDoDsr0=; b=EplnvrtGfiqw30Q7kLRL4IlET5brTvihBzdcPhwFcU52tuqzxiV8RsfpYLC6eqaRkT 0ygTR4IJES+0HuyXNrkvaMUB4MzL5aCtMFq4qLGCD5L9OSbFTnoOgXgJY3djH9ps5yNX adcAmozFjGsMnYIU8phDFbXr3kRqbQSN4JnIA= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:subject:date:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=xM+YcVXCVdAbnW4OE/73urNUlHdnFwO79q+gmDoDsr0=; b=zt8Z5FumYezLhMecp+WZKURcPJ5YkTRpiRgEE0wYxP2uuEZFRkal7k6VjYqKVDm4+g +dBgMtlTPtw7vsSaECygz3frwHNA4yDNVlFOZ9LNnbcihSgNm3oJctQQAyvtmRo4RQ5e JNctSEgtKiVdou5y8nfLrumAEnKS1zhxSQ9WZT18pit9T94wi/RnfkYeFjMMamSUI/gL znHeyT+yiB4URbe201kyYxT3IMAQJf+AAkRvig9+7t4VWlOj2E8p1cjBhIrLTFnkXCkI n9aKT1xd3pcTy+g2indacjnal1/y3WZZJ2nShou22YgLkY5+uWZXNVgqoB3q2tOfT7F+ FULA== X-Gm-Message-State: ANoB5pnKIytJvfOhSNSHRBhPE9DPKf0Q9xzuP6HZGDBT0GNoUgVe92tC V5KjlexZPc4iO2g7DlrHQ3DYJg== X-Google-Smtp-Source: AA0mqf4Ktnl0YrpUJ/zQ2j/nhucRmcyReeUSMGK8cfPoN0Q4ChIekjUj0rl3RtmuKDuhQbti/TNdjw== X-Received: by 2002:a17:906:cd0f:b0:78d:99ee:4e68 with SMTP id oz15-20020a170906cd0f00b0078d99ee4e68mr9829642ejb.302.1668431946244; Mon, 14 Nov 2022 05:19:06 -0800 (PST) Received: from alco.roam.corp.google.com ([2620:0:1059:10:c205:5c4e:7456:c8cc]) by smtp.gmail.com with ESMTPSA id g13-20020a50ec0d000000b0045b3853c4b7sm4802061edr.51.2022.11.14.05.19.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Nov 2022 05:19:05 -0800 (PST) From: Ricardo Ribalda Date: Mon, 14 Nov 2022 14:18:38 +0100 Subject: [PATCH v1 1/2] Documentation: sysctl: Correct kexec_load_disabled MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20221114-disable-kexec-reset-v1-1-fb51d20cf871@chromium.org> References: <20221114-disable-kexec-reset-v1-0-fb51d20cf871@chromium.org> In-Reply-To: <20221114-disable-kexec-reset-v1-0-fb51d20cf871@chromium.org> To: Eric Biederman , Jonathan Corbet Cc: Sergey Senozhatsky , linux-kernel@vger.kernel.org, kexec@lists.infradead.org, Ross Zwisler , linux-doc@vger.kernel.org, "Joel Fernandes (Google)" , Steven Rostedt , Ricardo Ribalda X-Mailer: b4 0.11.0-dev-d93f8 X-Developer-Signature: v=1; a=openpgp-sha256; l=1116; i=ribalda@chromium.org; h=from:subject:message-id; bh=zDOuQm9cQhkd/nA1jGZR3he7xVJj/YKQQUhyS/khFbk=; b=owEBbQKS/ZANAwAKAdE30T7POsSIAcsmYgBjckBEjyJCQEx200s9vD/3tqll0nVOqpN6FKcWu+uj NvYvTuSJAjMEAAEKAB0WIQREDzjr+/4oCDLSsx7RN9E+zzrEiAUCY3JARAAKCRDRN9E+zzrEiDnOD/ 9Ks9b+Ued+KyoeV7ygpZz76D9Q0XfAFOq0DMdz7krQNEYRNokkHIz2X1PLcF5UKgyWl3iu1ZY/OV4M YReDtofadyOBt+kFuZY1ziV9Ocyja87uU3rlZ5fcWJQfd/+8D0vBVgFL33ydaSHLhcvbrDqD2TCsuB kM9doysF+DrfnmS58H7WRPuNZd6ZOLnknvMvAG8vTJWx0iDkvnSfB7d5Xo0WT0bGZvIPLZE960yehp B9RePEIQ6nDcKNnD1azJDKCw/8XXlrYuzzLpXk4+sqUwQrbL88xnKMx39NWg3Xm4G3kIQtX3igfENS VomHElAGKHt3JpqVL50wJXWOHEa3Itlh+GBERvYeSsMTuH5Wa9V1JsQFLgurc3zrgWvV5c6hHrXm/4 rS8BR1x63yULYU4nA+1CRFS3wiv1hiMa/XNC85qbpxhSiYdT75dX7zOasM3pbuOGNtxzxvZVEVOpi6 D4uPlxgxKXvHOn69jKwVxMoSIL3+GTYT1ZCsIR65O3oIZpmyWdBEgrx+MGnagCP7ZHheb6ZHOqquHT m2euzpVJmeNS1Ity9c5+aVrkfHy7QPHTEcjrZ0MO5/jgsy6AFVWDT1bRqrRfO53GpsqvHWlgFwVjCK G7Pxt3W2v/SOThv+B7SYuaZU9foBvShbrFcw58wDACKF78S1+QVsLpFd7Feg== X-Developer-Key: i=ribalda@chromium.org; a=openpgp; fpr=9EC3BB66E2FC129A6F90B39556A0D81F9F782DA9 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org kexec_load_disabled affects both ``kexec_load`` and ``kexec_file_load`` syscalls. Make it explicit. Signed-off-by: Ricardo Ribalda diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/ad= min-guide/sysctl/kernel.rst index 98d1b198b2b4..97394bd9d065 100644 Acked-by: Baoquan He --- a/Documentation/admin-guide/sysctl/kernel.rst +++ b/Documentation/admin-guide/sysctl/kernel.rst @@ -450,9 +450,10 @@ this allows system administrators to override the kexec_load_disabled =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =20 -A toggle indicating if the ``kexec_load`` syscall has been disabled. -This value defaults to 0 (false: ``kexec_load`` enabled), but can be -set to 1 (true: ``kexec_load`` disabled). +A toggle indicating if the syscalls ``kexec_load`` and +``kexec_file_load`` have been disabled. +This value defaults to 0 (false: ``kexec_*load`` enabled), but can be +set to 1 (true: ``kexec_*load`` disabled). Once true, kexec can no longer be used, and the toggle cannot be set back to false. This allows a kexec image to be loaded before disabling the syscall, --=20 b4 0.11.0-dev-d93f8 From nobody Mon Apr 13 14:29:33 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3974EC433FE for ; Mon, 14 Nov 2022 13:20:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235843AbiKNNUA (ORCPT ); Mon, 14 Nov 2022 08:20:00 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46208 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237985AbiKNNTg (ORCPT ); Mon, 14 Nov 2022 08:19:36 -0500 Received: from mail-ej1-x635.google.com (mail-ej1-x635.google.com [IPv6:2a00:1450:4864:20::635]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AED1D2BB1B for ; Mon, 14 Nov 2022 05:19:07 -0800 (PST) Received: by mail-ej1-x635.google.com with SMTP id i10so19573599ejg.6 for ; Mon, 14 Nov 2022 05:19:07 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:subject:date:from:from:to:cc:subject:date:message-id :reply-to; bh=YBDqrK6ZdWq2OzrZLHJQraMMoPoinvhQP0W8u+3GcTk=; b=l+SRhUtVZVJ0JfZqzT7bi1gWoeK5gqgOT1cfNOL0iydr9/ACO4IBVNXucMwfahDafq CcjyAjAzeje8N09iCbh4cC4KqMlln1mN4sbG6gBrvQZZ4jUrmqPsT0sGID2YHiZfN3pG CoywAWz6UY5pqFVZHhmTJBgeSD1qak/cqkiWI= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:subject:date:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=YBDqrK6ZdWq2OzrZLHJQraMMoPoinvhQP0W8u+3GcTk=; b=GXgSJ78ljP7YhUGARctbwG8TYX7YlYOPh3fTCcK29+Dk/h3q8xoB5U7bHBLEIvNbmX Ewql84jdM+ub+Pund2jn8iKTtppuSJJvILB6VAE6u2gJgJvVQyg+SCw+Z6cFhFWjLiC3 9ojc0cvNN7iUv5LaRQGfj4PBryf9YLlm5JzGEHo/eRG4ZD5/1DclKEj5ewlyPmhikQzw b2fpL4ZRxK3ZQCq7333RKL3wGNWFTroHrFoSecTfqIQFES0QrpkFHE88FD6KtIhdu15M Cfi1vhijf5pqF8Z50YEfwUeKC6dWUf7N9zZFKx/Qa/dkF33Vc0NPsG+BBgjeo0Jk5SWt b6tg== X-Gm-Message-State: ANoB5pnzS2kSJSfZ58OpRPMXIqfrLkuvuPKt23tdv7+vVdC9ngFoVrRX lQbKRRgAfTjW3R00udd6fvuCRA== X-Google-Smtp-Source: AA0mqf5XEPlCqCerbKFCDqW7Ii2ijdR3SvE9imxd10P/fR2NMfFIZ1DEoLE/yUsvtR/op0wt/ZWzBA== X-Received: by 2002:a17:906:f208:b0:7ae:2277:9fec with SMTP id gt8-20020a170906f20800b007ae22779fecmr9990574ejb.623.1668431947306; Mon, 14 Nov 2022 05:19:07 -0800 (PST) Received: from alco.roam.corp.google.com ([2620:0:1059:10:c205:5c4e:7456:c8cc]) by smtp.gmail.com with ESMTPSA id g13-20020a50ec0d000000b0045b3853c4b7sm4802061edr.51.2022.11.14.05.19.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Nov 2022 05:19:06 -0800 (PST) From: Ricardo Ribalda Date: Mon, 14 Nov 2022 14:18:39 +0100 Subject: [PATCH v1 2/2] kexec: Introduce kexec_reboot_disabled MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20221114-disable-kexec-reset-v1-2-fb51d20cf871@chromium.org> References: <20221114-disable-kexec-reset-v1-0-fb51d20cf871@chromium.org> In-Reply-To: <20221114-disable-kexec-reset-v1-0-fb51d20cf871@chromium.org> To: Eric Biederman , Jonathan Corbet Cc: Sergey Senozhatsky , linux-kernel@vger.kernel.org, kexec@lists.infradead.org, Ross Zwisler , linux-doc@vger.kernel.org, "Joel Fernandes (Google)" , Steven Rostedt , Ricardo Ribalda X-Mailer: b4 0.11.0-dev-d93f8 X-Developer-Signature: v=1; a=openpgp-sha256; l=3808; i=ribalda@chromium.org; h=from:subject:message-id; bh=dblSayUsSfEKi8F2aGC75NJql5jVZbhwpLBwKIyAUtI=; b=owEBbQKS/ZANAwAKAdE30T7POsSIAcsmYgBjckBFo6eu9Gtv5tVzghpwemmGVrmtXYcngm/W6RxM 3Cx6NGiJAjMEAAEKAB0WIQREDzjr+/4oCDLSsx7RN9E+zzrEiAUCY3JARQAKCRDRN9E+zzrEiKEID/ 4te8B7uFehLdBDS2AiqR+VMunRK2lzXEeuVXblaP3r9ExwUMnGbUtAWttF2wal25J7+bvvo5sQnQWQ /BbODeZY+8zGMtVVZGYXtwZ9uGeX53xvh1fheLmkHVHxuKwB7TC3SsPxSIhDj+6M+9YbmEbrJe1YB5 VcCdjYyjDHo9YFjKOXDIQ/zrsYzhCpCX1xND0zKYlIe58zE+LkT6EGs47rw9I0GUdqRvbWDIa6MrlO cKE8iQAOX9ihR5wGRJVBO1O8+GBbq+3x7xfeEo4qYfJv64ne4t/TUXRAajUAg8mIZRlWp0/r9vAqB4 siXhXif6Sbr0P7D3ND5d5/e3A7vCy4jnIEAFnyoA2bMZp8lPtKa0OZ/CkIYVygBbymXYiwgMmqhs89 01cb4w3UOj810NTpXb1nR/D5wnH1A5jtHvp+09F+Js/8q5GPEDGqdaglAlE2fnATD07PdX/GD4xsDz vsqnw7M4vpGHQuPPzFizXXK8vTJIcJnmVpZJG7nX+s3QHH7FgAaUFC6yKYcFw/5aKqYEtHD1rCuLBf xPmpZ8s6CIzKx0kfixlh9mmR+pbwFC9QqULyccreqPocelwhaHSZXUZRvABk1AAkrFWRt39ChNVEOr g7LSeqsxViMsBQgX/QuEcRq4LGx/aHZOplyG/1DFFpu9P86p7zYC8a3U7sdw== X-Developer-Key: i=ribalda@chromium.org; a=openpgp; fpr=9EC3BB66E2FC129A6F90B39556A0D81F9F782DA9 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Create a new toogle that disables LINUX_REBOOT_CMD_KEXEC, reducing the attack surface to a system. Without this toogle, an attacker can only reboot into a different kernel if they can create a panic(). Signed-off-by: Ricardo Ribalda diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/ad= min-guide/sysctl/kernel.rst index 97394bd9d065..25d019682d33 100644 --- a/Documentation/admin-guide/sysctl/kernel.rst +++ b/Documentation/admin-guide/sysctl/kernel.rst @@ -462,6 +462,17 @@ altered. Generally used together with the `modules_disabled`_ sysctl. =20 =20 +kexec_reboot_disabled +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D + +A toggle indicating if ``LINUX_REBOOT_CMD_KEXEC`` has been disabled. +This value defaults to 0 (false: ``LINUX_REBOOT_CMD_KEXEC`` enabled), +but can be set to 1 (true: ``LINUX_REBOOT_CMD_KEXEC`` disabled). +Once true, kexec can no longer be used for reboot and the toggle +cannot be set back to false. +This toggle does not affect the use of kexec during a crash. + + kptr_restrict =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =20 diff --git a/include/linux/kexec.h b/include/linux/kexec.h index 41a686996aaa..15c3fad8918b 100644 --- a/include/linux/kexec.h +++ b/include/linux/kexec.h @@ -407,6 +407,7 @@ extern int kimage_crash_copy_vmcoreinfo(struct kimage *= image); extern struct kimage *kexec_image; extern struct kimage *kexec_crash_image; extern int kexec_load_disabled; +extern int kexec_reboot_disabled; =20 #ifndef kexec_flush_icache_page #define kexec_flush_icache_page(page) diff --git a/kernel/kexec.c b/kernel/kexec.c index cb8e6e6f983c..43063f803d81 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -196,6 +196,10 @@ static inline int kexec_load_check(unsigned long nr_se= gments, if (!capable(CAP_SYS_BOOT) || kexec_load_disabled) return -EPERM; =20 + /* Check if the system admin has disabled kexec reboot. */ + if (!(flags & KEXEC_ON_CRASH) && kexec_reboot_disabled) + return -EPERM; + /* Permit LSMs and IMA to fail the kexec */ result =3D security_kernel_load_data(LOADING_KEXEC_IMAGE, false); if (result < 0) diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c index ca2743f9c634..fe82e2525705 100644 --- a/kernel/kexec_core.c +++ b/kernel/kexec_core.c @@ -929,6 +929,7 @@ int kimage_load_segment(struct kimage *image, struct kimage *kexec_image; struct kimage *kexec_crash_image; int kexec_load_disabled; +int kexec_reboot_disabled; #ifdef CONFIG_SYSCTL static struct ctl_table kexec_core_sysctls[] =3D { { @@ -941,6 +942,16 @@ static struct ctl_table kexec_core_sysctls[] =3D { .extra1 =3D SYSCTL_ONE, .extra2 =3D SYSCTL_ONE, }, + { + .procname =3D "kexec_reboot_disabled", + .data =3D &kexec_reboot_disabled, + .maxlen =3D sizeof(int), + .mode =3D 0644, + /* only handle a transition from default "0" to "1" */ + .proc_handler =3D proc_dointvec_minmax, + .extra1 =3D SYSCTL_ONE, + .extra2 =3D SYSCTL_ONE, + }, { } }; =20 @@ -1138,7 +1149,7 @@ int kernel_kexec(void) =20 if (!kexec_trylock()) return -EBUSY; - if (!kexec_image) { + if (!kexec_image || kexec_reboot_disabled) { error =3D -EINVAL; goto Unlock; } diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c index 45637511e0de..583fba6de5cb 100644 --- a/kernel/kexec_file.c +++ b/kernel/kexec_file.c @@ -333,6 +333,11 @@ SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, = initrd_fd, if (!capable(CAP_SYS_BOOT) || kexec_load_disabled) return -EPERM; =20 + /* Check if the system admin has disabled kexec reboot. */ + if (!(flags & (KEXEC_FILE_ON_CRASH | KEXEC_FILE_UNLOAD)) + && kexec_reboot_disabled) + return -EPERM; + /* Make sure we have a legal set of flags */ if (flags !=3D (flags & KEXEC_FILE_FLAGS)) return -EINVAL; --=20 b4 0.11.0-dev-d93f8