Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S938927AbcJXNKB (ORCPT ); Mon, 24 Oct 2016 09:10:01 -0400 Received: from mail-wm0-f42.google.com ([74.125.82.42]:38091 "EHLO mail-wm0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935319AbcJXNJh (ORCPT ); Mon, 24 Oct 2016 09:09:37 -0400 Date: Mon, 24 Oct 2016 14:09:31 +0100 From: Matt Fleming To: Andy Lutomirski Cc: "linux-efi@vger.kernel.org" , Brian Gerst , "linux-tip-commits@vger.kernel.org" , Thomas Gleixner , Ingo Molnar , Linus Torvalds , Ard Biesheuvel , Josh Poimboeuf , Denys Vlasenko , "H. Peter Anvin" , "linux-kernel@vger.kernel.org" , Nadav Amit , Borislav Petkov , Peter Zijlstra Subject: Re: [tip:x86/asm] x86/mm/64: Enable vmapped stacks (CONFIG_HAVE_ARCH_VMAP_STACK=y) Message-ID: <20161024130931.GC20387@codeblueprint.co.uk> References: <20161021123243.GC27807@codeblueprint.co.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24+41 (02bc14ed1569) (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7912 Lines: 240 On Fri, 21 Oct, at 05:18:30PM, Andy Lutomirski wrote: > > This is asking for trouble if any of the variable length parameters > are on the stack. How about adding a "size_t size" parameter and > doing: > > if (!va) { > return 0; > } else if (virt_addr_valid(va)) { > return virt_to_phys(va); > } else { > /* A fully aligned variable on the stack is guaranteed not to cross > a page boundary. */ > WARN_ON(!IS_ALIGNED((uintptr_t)va, size) || size > PAGE_SIZE); > return slow_virt_to_phys(va); > } Ah, good catch. Something like this? --- >From d2c17f46686076677da3bf04caa2f69d654f8d8a Mon Sep 17 00:00:00 2001 From: Matt Fleming Date: Thu, 20 Oct 2016 22:17:21 +0100 Subject: [PATCH] x86/efi: Prevent mixed mode boot corruption with CONFIG_VMAP_STACK Booting an EFI mixed mode kernel has been crashing since commit: e37e43a497d5 ("x86/mm/64: Enable vmapped stacks (CONFIG_HAVE_ARCH_VMAP_STACK=y)") The user-visible effect in my test setup was the kernel being unable to find the root file system ramdisk. This was likely caused by silent memory or page table corruption. Enabling CONFIG_DEBUG_VIRTUAL immediately flagged the thunking code as abusing virt_to_phys() because it was passing addresses that were not part of the kernel direct mapping. Use the slow version instead, which correctly handles all memory regions by performing a page table walk. Suggested-by: Andy Lutomirski Cc: Ard Biesheuvel Cc: Ingo Molnar Cc: Thomas Gleixner Cc: "H. Peter Anvin" Signed-off-by: Matt Fleming --- arch/x86/platform/efi/efi_64.c | 79 +++++++++++++++++++++++++++++------------- 1 file changed, 55 insertions(+), 24 deletions(-) diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c index 58b0f801f66f..010544293dda 100644 --- a/arch/x86/platform/efi/efi_64.c +++ b/arch/x86/platform/efi/efi_64.c @@ -31,6 +31,7 @@ #include #include #include +#include #include #include @@ -211,11 +212,36 @@ void efi_sync_low_kernel_mappings(void) memcpy(pud_efi, pud_k, sizeof(pud_t) * num_entries); } +/* + * Wrapper for slow_virt_to_phys() that handles NULL addresses. + */ +static inline phys_addr_t +virt_to_phys_or_null_size(void *va, unsigned long size) +{ + if (!va) + return 0; + + if (virt_addr_valid(va)) + return virt_to_phys(va); + + /* + * A fully aligned variable on the stack is guaranteed not to + * cross a page bounary. + */ + WARN_ON(!IS_ALIGNED((unsigned long)va, size) || size > PAGE_SIZE); + + return slow_virt_to_phys(va); +} + +#define virt_to_phys_or_null(addr) \ + virt_to_phys_or_null_size((addr), sizeof(*(addr))) + int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages) { unsigned long pfn, text; struct page *page; unsigned npages; + void *addr; pgd_t *pgd; if (efi_enabled(EFI_OLD_MEMMAP)) @@ -251,7 +277,8 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages) if (!page) panic("Unable to allocate EFI runtime stack < 4GB\n"); - efi_scratch.phys_stack = virt_to_phys(page_address(page)); + addr = page_address(page); + efi_scratch.phys_stack = virt_to_phys_or_null_size(addr, PAGE_SIZE); efi_scratch.phys_stack += PAGE_SIZE; /* stack grows down */ npages = (_etext - _text) >> PAGE_SHIFT; @@ -494,8 +521,8 @@ static efi_status_t efi_thunk_get_time(efi_time_t *tm, efi_time_cap_t *tc) spin_lock(&rtc_lock); - phys_tm = virt_to_phys(tm); - phys_tc = virt_to_phys(tc); + phys_tm = virt_to_phys_or_null(tm); + phys_tc = virt_to_phys_or_null(tc); status = efi_thunk(get_time, phys_tm, phys_tc); @@ -511,7 +538,7 @@ static efi_status_t efi_thunk_set_time(efi_time_t *tm) spin_lock(&rtc_lock); - phys_tm = virt_to_phys(tm); + phys_tm = virt_to_phys_or_null(tm); status = efi_thunk(set_time, phys_tm); @@ -529,9 +556,9 @@ efi_thunk_get_wakeup_time(efi_bool_t *enabled, efi_bool_t *pending, spin_lock(&rtc_lock); - phys_enabled = virt_to_phys(enabled); - phys_pending = virt_to_phys(pending); - phys_tm = virt_to_phys(tm); + phys_enabled = virt_to_phys_or_null(enabled); + phys_pending = virt_to_phys_or_null(pending); + phys_tm = virt_to_phys_or_null(tm); status = efi_thunk(get_wakeup_time, phys_enabled, phys_pending, phys_tm); @@ -549,7 +576,7 @@ efi_thunk_set_wakeup_time(efi_bool_t enabled, efi_time_t *tm) spin_lock(&rtc_lock); - phys_tm = virt_to_phys(tm); + phys_tm = virt_to_phys_or_null(tm); status = efi_thunk(set_wakeup_time, enabled, phys_tm); @@ -558,6 +585,10 @@ efi_thunk_set_wakeup_time(efi_bool_t enabled, efi_time_t *tm) return status; } +static unsigned long efi_name_size(efi_char16_t *name) +{ + return ucs2_strsize(name, EFI_VAR_NAME_LEN) + 1; +} static efi_status_t efi_thunk_get_variable(efi_char16_t *name, efi_guid_t *vendor, @@ -567,11 +598,11 @@ efi_thunk_get_variable(efi_char16_t *name, efi_guid_t *vendor, u32 phys_name, phys_vendor, phys_attr; u32 phys_data_size, phys_data; - phys_data_size = virt_to_phys(data_size); - phys_vendor = virt_to_phys(vendor); - phys_name = virt_to_phys(name); - phys_attr = virt_to_phys(attr); - phys_data = virt_to_phys(data); + phys_data_size = virt_to_phys_or_null(data_size); + phys_vendor = virt_to_phys_or_null(vendor); + phys_name = virt_to_phys_or_null_size(name, efi_name_size(name)); + phys_attr = virt_to_phys_or_null(attr); + phys_data = virt_to_phys_or_null_size(data, *data_size); status = efi_thunk(get_variable, phys_name, phys_vendor, phys_attr, phys_data_size, phys_data); @@ -586,9 +617,9 @@ efi_thunk_set_variable(efi_char16_t *name, efi_guid_t *vendor, u32 phys_name, phys_vendor, phys_data; efi_status_t status; - phys_name = virt_to_phys(name); - phys_vendor = virt_to_phys(vendor); - phys_data = virt_to_phys(data); + phys_name = virt_to_phys_or_null_size(name, efi_name_size(name)); + phys_vendor = virt_to_phys_or_null(vendor); + phys_data = virt_to_phys_or_null_size(data, data_size); /* If data_size is > sizeof(u32) we've got problems */ status = efi_thunk(set_variable, phys_name, phys_vendor, @@ -605,9 +636,9 @@ efi_thunk_get_next_variable(unsigned long *name_size, efi_status_t status; u32 phys_name_size, phys_name, phys_vendor; - phys_name_size = virt_to_phys(name_size); - phys_vendor = virt_to_phys(vendor); - phys_name = virt_to_phys(name); + phys_name_size = virt_to_phys_or_null(name_size); + phys_vendor = virt_to_phys_or_null(vendor); + phys_name = virt_to_phys_or_null_size(name, *name_size); status = efi_thunk(get_next_variable, phys_name_size, phys_name, phys_vendor); @@ -621,7 +652,7 @@ efi_thunk_get_next_high_mono_count(u32 *count) efi_status_t status; u32 phys_count; - phys_count = virt_to_phys(count); + phys_count = virt_to_phys_or_null(count); status = efi_thunk(get_next_high_mono_count, phys_count); return status; @@ -633,7 +664,7 @@ efi_thunk_reset_system(int reset_type, efi_status_t status, { u32 phys_data; - phys_data = virt_to_phys(data); + phys_data = virt_to_phys_or_null_size(data, data_size); efi_thunk(reset_system, reset_type, status, data_size, phys_data); } @@ -661,9 +692,9 @@ efi_thunk_query_variable_info(u32 attr, u64 *storage_space, if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION) return EFI_UNSUPPORTED; - phys_storage = virt_to_phys(storage_space); - phys_remaining = virt_to_phys(remaining_space); - phys_max = virt_to_phys(max_variable_size); + phys_storage = virt_to_phys_or_null(storage_space); + phys_remaining = virt_to_phys_or_null(remaining_space); + phys_max = virt_to_phys_or_null(max_variable_size); status = efi_thunk(query_variable_info, attr, phys_storage, phys_remaining, phys_max); -- 2.10.0