From nobody Sun Feb 8 21:46:47 2026 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.21]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9AF36148FF3 for ; Thu, 15 Feb 2024 23:14:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.21 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708038883; cv=none; b=VZT/hCbxpbHjYsnGoaPRpuVzb51wqrDGqovl3wP0Ik1HddDZgowwxo+BSU/TzfxXgCo5aJJi0R3E8NFXbrzOYr4SHV1419n5BUHgXS5NOgRgfaGlP2chZNDmYct7bdDYxakab9S6Ie9WN5HQ4lzVaiKh5KRUP6Df2wF1PrYADfc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708038883; c=relaxed/simple; bh=unKAy/CGTalz/NFNrhf3RgWUr6Aw4RHxK63+GyNg8+4=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version:Content-Type; b=Y2Hj9zuPVxwpqcplg2o9BNvbx/EMUzorMlGT1ne+LX724DtfReTPlZi/YL+1iNat2SPbCLeyjR2kzZDGEidiJ+HpvQ1IABvq6SPPIdWfuLhumnfsymVbWmePxCLswyNC05ZAVFfWFc7boF/f6JTe385mG8TB3YP7dgJygvCx6z0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=YM/GTh8e; arc=none smtp.client-ip=198.175.65.21 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="YM/GTh8e" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1708038882; x=1739574882; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=unKAy/CGTalz/NFNrhf3RgWUr6Aw4RHxK63+GyNg8+4=; b=YM/GTh8eK6mmi7U9ztodoNavv2KsLhrv/Sw40BG7ed/5Y/ArNFlMiQdt AhW1OAnRzD+XSqg6dVq8RnXL+IipxMwuQwAYURyYBG3zf3jgjuhj+wvz0 MuUNearUX/GMA0y0QSBUp5mi4/0IreoGqW5jWJo8zQKvGcPCF3FqI0dNT kvCkrS8Kc/CJNaqxDwqNCMpB9+W69FXpZHVlmGLY9gigJThblFJTyIta3 ZHd4h9FL3YPa2Z1P+9ktN5/M+8KUwLGNv98cGw5JgsXby+lBzJDubLQne 5xoie9YIb97VNby7QW8BuQtfaNuQLrq0Y2aHHCu3dqiZKtGWLzYYfPz/+ Q==; X-IronPort-AV: E=McAfee;i="6600,9927,10985"; a="2066341" X-IronPort-AV: E=Sophos;i="6.06,162,1705392000"; d="scan'208";a="2066341" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by orvoesa113.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Feb 2024 15:14:40 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10985"; a="912250194" X-IronPort-AV: E=Sophos;i="6.06,162,1705392000"; d="scan'208";a="912250194" Received: from yshin-mobl1.amr.corp.intel.com (HELO rpedgeco-desk4.intel.com) ([10.209.95.133]) by fmsmga002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Feb 2024 15:14:39 -0800 From: Rick Edgecombe To: Liam.Howlett@oracle.com, akpm@linux-foundation.org, debug@rivosinc.com, broonie@kernel.org, kirill.shutemov@linux.intel.com, keescook@chromium.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, luto@kernel.org, peterz@infradead.org, hpa@zytor.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: rick.p.edgecombe@intel.com Subject: [RFC PATCH 3/8] mm: Use get_unmapped_area_vmflags() Date: Thu, 15 Feb 2024 15:13:27 -0800 Message-Id: <20240215231332.1556787-4-rick.p.edgecombe@intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240215231332.1556787-1-rick.p.edgecombe@intel.com> References: <20240215231332.1556787-1-rick.p.edgecombe@intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable When memory is being placed, mmap() will take care to respect the guard gaps of certain types of memory (VM_SHADOWSTACK, VM_GROWSUP and VM_GROWSDOWN). In order to ensure guard gaps between mappings, mmap() needs to consider two things: 1. That the new mapping isn=E2=80=99t placed in an any existing mappings g= uard gaps. 2. That the new mapping isn=E2=80=99t placed such that any existing mappin= gs are not in *its* guard gaps. The long standing behavior of mmap() is to ensure 1, but not take any care around 2. So for example, if there is a PAGE_SIZE free area, and a mmap() with a PAGE_SIZE size, and a type that has a guard gap is being placed, mmap() may place the shadow stack in the PAGE_SIZE free area. Then the mapping that is supposed to have a guard gap will not have a gap to the adjacent VMA. Use mm_get_unmapped_area_vmflags() in the do_mmap() so future changes can cause shadow stack mappings to be placed with a guard gap. Also use the THP variant that takes vm_flags, such that THP shadow stack can get the same treatment. Adjust the vm_flags calculation to happen earlier so that the vm_flags can be passed into __get_unmapped_area(). Signed-off-by: Rick Edgecombe --- include/linux/mm.h | 2 ++ mm/mmap.c | 38 ++++++++++++++++++++++---------------- 2 files changed, 24 insertions(+), 16 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index da5219b48d52..9addf16dbf18 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -3352,6 +3352,8 @@ unsigned long randomize_stack_top(unsigned long stack= _top); unsigned long randomize_page(unsigned long start, unsigned long range); =20 extern unsigned long get_unmapped_area(struct file *, unsigned long, unsig= ned long, unsigned long, unsigned long); +extern unsigned long __get_unmapped_area(struct file *, unsigned long, uns= igned long, + unsigned long, unsigned long, vm_flags_t); =20 extern unsigned long mmap_region(struct file *file, unsigned long addr, unsigned long len, vm_flags_t vm_flags, unsigned long pgoff, diff --git a/mm/mmap.c b/mm/mmap.c index 2021bc040e81..2723f26f7c62 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1249,18 +1249,6 @@ unsigned long do_mmap(struct file *file, unsigned lo= ng addr, if (mm->map_count > sysctl_max_map_count) return -ENOMEM; =20 - /* Obtain the address to map to. we verify (or select) it and ensure - * that it represents a valid section of the address space. - */ - addr =3D get_unmapped_area(file, addr, len, pgoff, flags); - if (IS_ERR_VALUE(addr)) - return addr; - - if (flags & MAP_FIXED_NOREPLACE) { - if (find_vma_intersection(mm, addr, addr + len)) - return -EEXIST; - } - if (prot =3D=3D PROT_EXEC) { pkey =3D execute_only_pkey(mm); if (pkey < 0) @@ -1274,6 +1262,18 @@ unsigned long do_mmap(struct file *file, unsigned lo= ng addr, vm_flags |=3D calc_vm_prot_bits(prot, pkey) | calc_vm_flag_bits(flags) | mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC; =20 + /* Obtain the address to map to. we verify (or select) it and ensure + * that it represents a valid section of the address space. + */ + addr =3D __get_unmapped_area(file, addr, len, pgoff, flags, vm_flags); + if (IS_ERR_VALUE(addr)) + return addr; + + if (flags & MAP_FIXED_NOREPLACE) { + if (find_vma_intersection(mm, addr, addr + len)) + return -EEXIST; + } + if (flags & MAP_LOCKED) if (!can_do_mlock()) return -EPERM; @@ -1831,8 +1831,8 @@ unsigned long mm_get_unmapped_area_vmflags(struct mm_= struct *mm, struct file *fi } =20 unsigned long -get_unmapped_area(struct file *file, unsigned long addr, unsigned long len, - unsigned long pgoff, unsigned long flags) +__get_unmapped_area(struct file *file, unsigned long addr, unsigned long l= en, + unsigned long pgoff, unsigned long flags, vm_flags_t vm_flags) { unsigned long (*get_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long) @@ -1865,8 +1865,8 @@ get_unmapped_area(struct file *file, unsigned long ad= dr, unsigned long len, if (get_area) addr =3D get_area(file, addr, len, pgoff, flags); else - addr =3D mm_get_unmapped_area(current->mm, file, addr, len, - pgoff, flags); + addr =3D mm_get_unmapped_area_vmflags(current->mm, file, addr, len, + pgoff, flags, vm_flags); if (IS_ERR_VALUE(addr)) return addr; =20 @@ -1879,6 +1879,12 @@ get_unmapped_area(struct file *file, unsigned long a= ddr, unsigned long len, return error ? error : addr; } =20 +unsigned long +get_unmapped_area(struct file *file, unsigned long addr, unsigned long len, + unsigned long pgoff, unsigned long flags) +{ + return __get_unmapped_area(file, addr, len, pgoff, flags, 0); +} EXPORT_SYMBOL(get_unmapped_area); =20 unsigned long --=20 2.34.1