From nobody Fri Dec 19 01:49:44 2025 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 2FF3CC83F1D for ; Mon, 28 Aug 2023 15:10:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232490AbjH1PJn (ORCPT ); Mon, 28 Aug 2023 11:09:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49426 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231284AbjH1PJV (ORCPT ); Mon, 28 Aug 2023 11:09:21 -0400 Received: from mail-wm1-x32d.google.com (mail-wm1-x32d.google.com [IPv6:2a00:1450:4864:20::32d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1FDC21AA for ; Mon, 28 Aug 2023 08:09:16 -0700 (PDT) Received: by mail-wm1-x32d.google.com with SMTP id 5b1f17b1804b1-4013454fa93so28875295e9.0 for ; Mon, 28 Aug 2023 08:09:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1693235354; x=1693840154; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=QXssY8R3UfI51/fzerFRXliKac0QknXs4XkU/07pT5E=; b=TXgobUHzdy1/oc00DCkfPuEhJu9AWsZDH7ItfMlZ9px/6av7xSZfC0WrjhZ16H5vnH +BXZsUMOLMGBNanD+Ods+R3MJffoWBq5sR8yyAUkuszZbSoBMR1IFcOLTFENcXg98b7t Yahy0kl0OhvBiWJFAmjSAeDAGABOGBOn3jPxs= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1693235354; x=1693840154; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=QXssY8R3UfI51/fzerFRXliKac0QknXs4XkU/07pT5E=; b=CEjxxbfcbIMn7C4ZcVN33X1Y4/5avd/9S/7OE+djoLG3TdQkj4Lo2unoRGVRagR73A vrOU5HLH2I3Ggk4ok+dYiS5rULVXjLcK8U2G7OAajVnRDAHJSPQIhlsv9OpfVKGoWcrI qvJJuMU3BtBhZD8Mgk84hRlSy5PQ0wgb59XvoCAv95CmkXgCRCW/pIcTfmcJna/GRXPM 0zcDxZKJ2RMy6HhPBTcS1WtUpZiUSqW8tmLziXb8gH/9TIhsdnDT0vnx3ckklEoBhUZ+ 0YbkyJo3jW0gDLj3HRWq6HM8GjE/JMx44DFHMIKr/mkT1Hc9y6jZrP59pHMaeLz49UsA UgwQ== X-Gm-Message-State: AOJu0YxTgJiRkMk0JcDd3nyniu3akR+GrpYK5sN0/eHxaCAdoUai8xGH KHHijQ2NuhgYdFKmWcPF8of3PR/sjsvvP5nAR/M= X-Google-Smtp-Source: AGHT+IGqMEI1E4b+HWptK+/EKjF7xI4VmzXlfBLXmqDJvfgj+65VugBjpc0Hy94kYyiGhQQdqXzgkQ== X-Received: by 2002:a1c:7508:0:b0:3fb:739d:27b2 with SMTP id o8-20020a1c7508000000b003fb739d27b2mr19489637wmc.8.1693235354252; Mon, 28 Aug 2023 08:09:14 -0700 (PDT) Received: from revest.zrh.corp.google.com ([2a00:79e0:9d:6:40c6:6cff:63b:c70a]) by smtp.gmail.com with ESMTPSA id v3-20020a5d43c3000000b003140fff4f75sm10730522wrr.17.2023.08.28.08.09.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Aug 2023 08:09:13 -0700 (PDT) From: Florent Revest To: linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: akpm@linux-foundation.org, catalin.marinas@arm.com, anshuman.khandual@arm.com, joey.gouly@arm.com, mhocko@suse.com, keescook@chromium.org, david@redhat.com, peterx@redhat.com, izbyshev@ispras.ru, broonie@kernel.org, szabolcs.nagy@arm.com, kpsingh@kernel.org, gthelen@google.com, toiwoton@gmail.com, ayush.jain3@amd.com, Florent Revest Subject: [PATCH v4 5/6] mm: Add a NO_INHERIT flag to the PR_SET_MDWE prctl Date: Mon, 28 Aug 2023 17:08:57 +0200 Message-ID: <20230828150858.393570-6-revest@chromium.org> X-Mailer: git-send-email 2.42.0.rc2.253.gd59a3bf2b4-goog In-Reply-To: <20230828150858.393570-1-revest@chromium.org> References: <20230828150858.393570-1-revest@chromium.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" This extends the current PR_SET_MDWE prctl arg with a bit to indicate that the process doesn't want MDWE protection to propagate to children. To implement this no-inherit mode, the tag in current->mm->flags must be absent from MMF_INIT_MASK. This means that the encoding for "MDWE but without inherit" is different in the prctl than in the mm flags. This leads to a bit of bit-mangling in the prctl implementation. Reviewed-by: Kees Cook Reviewed-by: Catalin Marinas Signed-off-by: Florent Revest --- include/linux/sched/coredump.h | 10 ++++++++++ include/uapi/linux/prctl.h | 1 + kernel/fork.c | 2 +- kernel/sys.c | 32 ++++++++++++++++++++++++++------ tools/include/uapi/linux/prctl.h | 1 + 5 files changed, 39 insertions(+), 7 deletions(-) diff --git a/include/linux/sched/coredump.h b/include/linux/sched/coredump.h index 0ee96ea7a0e9..1b37fa8fc723 100644 --- a/include/linux/sched/coredump.h +++ b/include/linux/sched/coredump.h @@ -91,4 +91,14 @@ static inline int get_dumpable(struct mm_struct *mm) MMF_DISABLE_THP_MASK | MMF_HAS_MDWE_MASK) =20 #define MMF_VM_MERGE_ANY 29 +#define MMF_HAS_MDWE_NO_INHERIT 30 + +static inline unsigned long mmf_init_flags(unsigned long flags) +{ + if (flags & (1UL << MMF_HAS_MDWE_NO_INHERIT)) + flags &=3D ~((1UL << MMF_HAS_MDWE) | + (1UL << MMF_HAS_MDWE_NO_INHERIT)); + return flags & MMF_INIT_MASK; +} + #endif /* _LINUX_SCHED_COREDUMP_H */ diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h index 9a85c69782bd..370ed14b1ae0 100644 --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -284,6 +284,7 @@ struct prctl_mm_map { /* Memory deny write / execute */ #define PR_SET_MDWE 65 # define PR_MDWE_REFUSE_EXEC_GAIN (1UL << 0) +# define PR_MDWE_NO_INHERIT (1UL << 1) =20 #define PR_GET_MDWE 66 =20 diff --git a/kernel/fork.c b/kernel/fork.c index 7b8b63fb0438..9da5a1192c98 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1285,7 +1285,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm= , struct task_struct *p, hugetlb_count_init(mm); =20 if (current->mm) { - mm->flags =3D current->mm->flags & MMF_INIT_MASK; + mm->flags =3D mmf_init_flags(current->mm->flags); mm->def_flags =3D current->mm->def_flags & VM_INIT_DEF_MASK; } else { mm->flags =3D default_dump_filter; diff --git a/kernel/sys.c b/kernel/sys.c index 2410e3999ebe..4a8073c1b255 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -2368,19 +2368,41 @@ static int prctl_set_vma(unsigned long opt, unsigne= d long start, } #endif /* CONFIG_ANON_VMA_NAME */ =20 +static inline unsigned long get_current_mdwe(void) +{ + unsigned long ret =3D 0; + + if (test_bit(MMF_HAS_MDWE, ¤t->mm->flags)) + ret |=3D PR_MDWE_REFUSE_EXEC_GAIN; + if (test_bit(MMF_HAS_MDWE_NO_INHERIT, ¤t->mm->flags)) + ret |=3D PR_MDWE_NO_INHERIT; + + return ret; +} + static inline int prctl_set_mdwe(unsigned long bits, unsigned long arg3, unsigned long arg4, unsigned long arg5) { + unsigned long current_bits; + if (arg3 || arg4 || arg5) return -EINVAL; =20 - if (bits & ~(PR_MDWE_REFUSE_EXEC_GAIN)) + if (bits & ~(PR_MDWE_REFUSE_EXEC_GAIN | PR_MDWE_NO_INHERIT)) + return -EINVAL; + + /* NO_INHERIT only makes sense with REFUSE_EXEC_GAIN */ + if (bits & PR_MDWE_NO_INHERIT && !(bits & PR_MDWE_REFUSE_EXEC_GAIN)) return -EINVAL; =20 + current_bits =3D get_current_mdwe(); + if (current_bits && current_bits !=3D bits) + return -EPERM; /* Cannot unset the flags */ + + if (bits & PR_MDWE_NO_INHERIT) + set_bit(MMF_HAS_MDWE_NO_INHERIT, ¤t->mm->flags); if (bits & PR_MDWE_REFUSE_EXEC_GAIN) set_bit(MMF_HAS_MDWE, ¤t->mm->flags); - else if (test_bit(MMF_HAS_MDWE, ¤t->mm->flags)) - return -EPERM; /* Cannot unset the flag */ =20 return 0; } @@ -2390,9 +2412,7 @@ static inline int prctl_get_mdwe(unsigned long arg2, = unsigned long arg3, { if (arg2 || arg3 || arg4 || arg5) return -EINVAL; - - return test_bit(MMF_HAS_MDWE, ¤t->mm->flags) ? - PR_MDWE_REFUSE_EXEC_GAIN : 0; + return get_current_mdwe(); } =20 static int prctl_get_auxv(void __user *addr, unsigned long len) diff --git a/tools/include/uapi/linux/prctl.h b/tools/include/uapi/linux/pr= ctl.h index 9a85c69782bd..370ed14b1ae0 100644 --- a/tools/include/uapi/linux/prctl.h +++ b/tools/include/uapi/linux/prctl.h @@ -284,6 +284,7 @@ struct prctl_mm_map { /* Memory deny write / execute */ #define PR_SET_MDWE 65 # define PR_MDWE_REFUSE_EXEC_GAIN (1UL << 0) +# define PR_MDWE_NO_INHERIT (1UL << 1) =20 #define PR_GET_MDWE 66 =20 --=20 2.42.0.rc2.253.gd59a3bf2b4-goog