From nobody Wed Dec 31 00:37:09 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 3F1CAC4167D for ; Mon, 13 Nov 2023 10:13:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229588AbjKMKNJ (ORCPT ); Mon, 13 Nov 2023 05:13:09 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37210 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229546AbjKMKNI (ORCPT ); Mon, 13 Nov 2023 05:13:08 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 38327D79; Mon, 13 Nov 2023 02:13:02 -0800 (PST) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 67EA3C433C8; Mon, 13 Nov 2023 10:13:00 +0000 (UTC) Date: Mon, 13 Nov 2023 11:12:57 +0100 From: Helge Deller To: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-parisc@vger.kernel.org Cc: matoro Subject: [PATCH] parisc: Fix mmap_base calculation when stack grows upwards Message-ID: MIME-Version: 1.0 Content-Disposition: inline Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Matoro reported various userspace crashes on the parisc platform with kernel 6.6 and bisected it to commit 3033cd430768 ("parisc: Use generic mmap top-d= own layout and brk randomization"). That commit switched parisc to use the common infrastructure to calculate mmap_base, but missed that the mmap_base() function takes care for architectures where the stack grows downwards only. Fix the mmap_base() calculation to include the stack-grows-upwards case and thus fix the userspace crashes on parisc. Reported-by: matoro Signed-off-by: Helge Deller Tested-by: matoro Fixes: 3033cd430768 ("parisc: Use generic mmap top-down layout and brk rand= omization") Cc: # v6.6+ diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig index fd69dfa0cdab..a7c9c0e69e5a 100644 --- a/arch/parisc/Kconfig +++ b/arch/parisc/Kconfig @@ -140,11 +140,11 @@ config ARCH_MMAP_RND_COMPAT_BITS_MIN default 8 =20 config ARCH_MMAP_RND_BITS_MAX - default 24 if 64BIT - default 17 + default 18 if 64BIT + default 13 =20 config ARCH_MMAP_RND_COMPAT_BITS_MAX - default 17 + default 13 =20 # unless you want to implement ACPI on PA-RISC ... ;-) config PM diff --git a/arch/parisc/include/asm/elf.h b/arch/parisc/include/asm/elf.h index 140eaa97bf21..2d73d3c3cd37 100644 --- a/arch/parisc/include/asm/elf.h +++ b/arch/parisc/include/asm/elf.h @@ -349,15 +349,7 @@ struct pt_regs; /* forward declaration... */ =20 #define ELF_HWCAP 0 =20 -/* Masks for stack and mmap randomization */ -#define BRK_RND_MASK (is_32bit_task() ? 0x07ffUL : 0x3ffffUL) -#define MMAP_RND_MASK (is_32bit_task() ? 0x1fffUL : 0x3ffffUL) -#define STACK_RND_MASK MMAP_RND_MASK - -struct mm_struct; -extern unsigned long arch_randomize_brk(struct mm_struct *); -#define arch_randomize_brk arch_randomize_brk - +#define STACK_RND_MASK 0x7ff /* 8MB of VA */ =20 #define ARCH_HAS_SETUP_ADDITIONAL_PAGES 1 struct linux_binprm; diff --git a/arch/parisc/include/asm/processor.h b/arch/parisc/include/asm/= processor.h index c05d121cf5d0..982aca20f56f 100644 --- a/arch/parisc/include/asm/processor.h +++ b/arch/parisc/include/asm/processor.h @@ -47,6 +47,8 @@ =20 #ifndef __ASSEMBLY__ =20 +struct rlimit; +unsigned long mmap_upper_limit(struct rlimit *rlim_stack); unsigned long calc_max_stack_size(unsigned long stack_max); =20 /* diff --git a/arch/parisc/kernel/sys_parisc.c b/arch/parisc/kernel/sys_paris= c.c index ab896eff7a1d..98af719d5f85 100644 --- a/arch/parisc/kernel/sys_parisc.c +++ b/arch/parisc/kernel/sys_parisc.c @@ -77,7 +77,7 @@ unsigned long calc_max_stack_size(unsigned long stack_max) * indicating that "current" should be used instead of a passed-in * value from the exec bprm as done with arch_pick_mmap_layout(). */ -static unsigned long mmap_upper_limit(struct rlimit *rlim_stack) +unsigned long mmap_upper_limit(struct rlimit *rlim_stack) { unsigned long stack_base; =20 diff --git a/mm/util.c b/mm/util.c index aa01f6ea5a75..744b4d7e3fae 100644 --- a/mm/util.c +++ b/mm/util.c @@ -414,6 +414,15 @@ static int mmap_is_legacy(struct rlimit *rlim_stack) =20 static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stac= k) { +#ifdef CONFIG_STACK_GROWSUP + /* + * For an upwards growing stack the calculation is much simpler. + * Memory for the maximum stack size is reserved at the top of the + * task. mmap_base starts directly below the stack and grows + * downwards. + */ + return PAGE_ALIGN_DOWN(mmap_upper_limit(rlim_stack) - rnd); +#else unsigned long gap =3D rlim_stack->rlim_cur; unsigned long pad =3D stack_guard_gap; =20 @@ -431,6 +440,7 @@ static unsigned long mmap_base(unsigned long rnd, struc= t rlimit *rlim_stack) gap =3D MAX_GAP; =20 return PAGE_ALIGN(STACK_TOP - gap - rnd); +#endif } =20 void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)