From nobody Mon Feb 9 00:54:51 2026 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.16]) (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 C1316839E8 for ; Tue, 26 Mar 2024 02:17:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.16 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711419441; cv=none; b=BfBw3L3QDMDYNlPs1jjpx4sJEyVhWREZWp3tkrTwTLCaUop5CPdq3rRhCn+wheoDmfppecoV6ev26P8WuNJqm8wCd31e3t+FXOrl2tdmzDXoG0yyD3NfsBF3xaHV1euUluD4sCOOCcd9SlMAXiIUqPRgI+TxeQmqQxvmyV014ws= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711419441; c=relaxed/simple; bh=Bt/iCncZprnekNGl7/DyAAsQ7Fn3bf5rVZDGMJUr1K4=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version:Content-Type; b=GdKhC9qzbMH6UQQUElYru9QIgGeqZtJL6m4mTZqS37XW+JvhKLPbGmQnMOIRzCZ+g5wI4YoGcbOVBgTmsQ2Z7ouV9GTDgwTajhsGxhXG/2gMlwhektgIpM3ZN26KQOO2rMbyMO6OSD0QeaxifksB59eMUi+MADmjo83Xw6zzQtA= 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=Lkdm4LcS; arc=none smtp.client-ip=198.175.65.16 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="Lkdm4LcS" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1711419440; x=1742955440; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=Bt/iCncZprnekNGl7/DyAAsQ7Fn3bf5rVZDGMJUr1K4=; b=Lkdm4LcSQ5+9KGpu5/rYceOBiYWxnVvcdj983C6t4hHrgvPy52S8hppp ShSSHkzPlmtffuGvMA5Y2yqmvKVneKJi3aZXQyHeXMV7AVmJKpTd8Edbw IUG8HeZKMZin24gbYVjFQaEEgQACl2ZaPpHDwh4IYgPSeqFKFEKkPs2zC IrNAsApCC4QMhFlk7MUjdOoDRWgf7VU6NcsBocMbv0DzEPMIhOIRb13qX 5/QS2Bv7dYDAqxLDKEHgcmMmKmIw//Cye/TlbgS7dNWed0OHggcEWcIi3 I+Ni6A154JB8l8AcLMhYWdHuk/ByR1wtwnmtVmpFlsCfI1kqw6cFiT5ZP w==; X-IronPort-AV: E=McAfee;i="6600,9927,11024"; a="6564259" X-IronPort-AV: E=Sophos;i="6.07,154,1708416000"; d="scan'208";a="6564259" Received: from orviesa004.jf.intel.com ([10.64.159.144]) by orvoesa108.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Mar 2024 19:17:15 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.07,154,1708416000"; d="scan'208";a="20489883" Received: from rpwilson-mobl.amr.corp.intel.com (HELO rpedgeco-desk4.intel.com) ([10.251.11.187]) by orviesa004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Mar 2024 19:17:15 -0700 From: Rick Edgecombe To: Liam.Howlett@oracle.com, akpm@linux-foundation.org, bp@alien8.de, broonie@kernel.org, christophe.leroy@csgroup.eu, 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 Cc: rick.p.edgecombe@intel.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v4 05/14] mm: Use get_unmapped_area_vmflags() Date: Mon, 25 Mar 2024 19:16:47 -0700 Message-Id: <20240326021656.202649-6-rick.p.edgecombe@intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240326021656.202649-1-rick.p.edgecombe@intel.com> References: <20240326021656.202649-1-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 --- v4: - Split removal of get_unmapped_area() export into a separate patch (Christophe Leroy) v2: - Make get_unmapped_area() a static inline (Kirill) --- include/linux/mm.h | 11 ++++++++++- mm/mmap.c | 32 ++++++++++++++++---------------- 2 files changed, 26 insertions(+), 17 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 0436b919f1c7..8b13cd891b53 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -3383,7 +3383,16 @@ 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 d160e88b1b1e..68b5bfcebadd 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1255,18 +1255,6 @@ 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) @@ -1280,6 +1268,18 @@ 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; @@ -1837,8 +1837,8 @@ 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) @@ -1873,8 +1873,8 @@ 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 --=20 2.34.1