From nobody Mon Feb 9 07:20:08 2026 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.15]) (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 C362D14402C for ; Tue, 12 Mar 2024 22:29:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.15 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710282548; cv=none; b=YdkXZwyrDB0akCbQ9oR/k0Ixk8gkVSdqBdQAGfqbMR9A1wh2QWR8L6JNhrHg+uLp9SYJV5BPanCX+pUjj21M10xvukvj1wRfC5G+iFJJheyfkkIMtIeRYGiFK07KSU1TsHtvMdzBNkVrjsxMNRgP9kn1zuMJuAue9Dm6KGs+4Rc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710282548; c=relaxed/simple; bh=/il3sOjTRp5Oqe4q9Enzhux+EAXqchUHAcOIqSHR2bA=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version:Content-Type; b=VPMw5ovsDDMsFPLQ3/5jt82CSX/t9gJVPwJDUtde0GmuIHeRemg652ozGprAUALCBlwkR3b+wv2NQqTBJrOg24vO9o2kHphJ6gVO1m+aKdfhifhS81VJ7b49yVvu2H+3PJRmJU/LlfOuD8nBDwxqIDY7WzjxMz6GgoBHiZp3cnA= 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=C3fpnPCu; arc=none smtp.client-ip=192.198.163.15 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="C3fpnPCu" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1710282547; x=1741818547; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=/il3sOjTRp5Oqe4q9Enzhux+EAXqchUHAcOIqSHR2bA=; b=C3fpnPCucoLFrq2Y6zSxDbF9HXdm/TZZol6ntgrNRmy+suJDltn1ATa2 lDctq6FFVHRm0pZK3vekCK2owD9aszky5cXA/vh9MvZW/2UcgA1GWF2Yr 7u/uzb1+aXRUXVGIvp4NNRAmJuENRlKu+5TNAUVuQ46vb0aF14WwvITkA m2OW6CtwVdBi1wmHIg0UdKpp+a457sv6d8sntP0ZrrXSkURrGGRcceitQ l1EV1BKCsblBpM3slZW5ROMPO/I31iu4gCFdW9Q1IzCrrIA3J3FVq26tz nQ9sVnMmEhMQdXFfQiFCXMBQ9wQhLCsfOnnct5ZBV8vAtl7ndPUeK23Qo Q==; X-IronPort-AV: E=McAfee;i="6600,9927,11011"; a="5191946" X-IronPort-AV: E=Sophos;i="6.07,119,1708416000"; d="scan'208";a="5191946" Received: from orviesa004.jf.intel.com ([10.64.159.144]) by fmvoesa109.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Mar 2024 15:29:02 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.07,119,1708416000"; d="scan'208";a="16356836" Received: from gargayus-mobl1.amr.corp.intel.com (HELO rpedgeco-desk4.intel.com) ([10.255.231.196]) by orviesa004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Mar 2024 15:29:02 -0700 From: Rick Edgecombe To: Liam.Howlett@oracle.com, akpm@linux-foundation.org, bp@alien8.de, broonie@kernel.org, dave.hansen@linux.intel.com, debug@rivosinc.com, hpa@zytor.com, keescook@chromium.org, kirill.shutemov@linux.intel.com, luto@kernel.org, mingo@redhat.com, peterz@infradead.org, tglx@linutronix.de, x86@kernel.org, christophe.leroy@csgroup.eu Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, rick.p.edgecombe@intel.com Subject: [PATCH v3 03/12] mm: Use get_unmapped_area_vmflags() Date: Tue, 12 Mar 2024 15:28:34 -0700 Message-Id: <20240312222843.2505560-4-rick.p.edgecombe@intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240312222843.2505560-1-rick.p.edgecombe@intel.com> References: <20240312222843.2505560-1-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 Reviewed-by: Christophe Leroy --- v2: - Make get_unmapped_area() a static inline (Kirill) --- include/linux/mm.h | 11 ++++++++++- mm/mmap.c | 34 ++++++++++++++++------------------ 2 files changed, 26 insertions(+), 19 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index f5a97dec5169..d91cde79aaee 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -3363,7 +3363,16 @@ extern int install_special_mapping(struct mm_struct = *mm, 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); +unsigned long +__get_unmapped_area(struct file *file, unsigned long addr, unsigned long l= en, + unsigned long pgoff, unsigned long flags, vm_flags_t vm_flags); + +static inline 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); +} =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 e23ce8ca24c9..a3128ed26676 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1257,18 +1257,6 @@ 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) @@ -1282,6 +1270,18 @@ 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; @@ -1839,8 +1839,8 @@ 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) @@ -1875,8 +1875,8 @@ 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 @@ -1889,8 +1889,6 @@ get_unmapped_area(struct file *file, unsigned long ad= dr, unsigned long len, return error ? error : addr; } =20 -EXPORT_SYMBOL(get_unmapped_area); - unsigned long mm_get_unmapped_area(struct mm_struct *mm, struct file *file, unsigned long addr, unsigned long len, --=20 2.34.1