Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752870AbcKGM6x (ORCPT ); Mon, 7 Nov 2016 07:58:53 -0500 Received: from mail-wm0-f41.google.com ([74.125.82.41]:38060 "EHLO mail-wm0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752427AbcKGM6w (ORCPT ); Mon, 7 Nov 2016 07:58:52 -0500 Date: Mon, 7 Nov 2016 12:32:14 +0000 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: <20161107123214.GG8845@codeblueprint.co.uk> References: <20161021123243.GC27807@codeblueprint.co.uk> <20161024130931.GC20387@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: 8162 Lines: 239 On Sun, 30 Oct, at 09:21:29AM, Andy Lutomirski wrote: > > @@ -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); > > This can't be on the stack -- you just allocated it with alloc_page(). Oh good point. I was too eager with search and replace. > > +static unsigned long efi_name_size(efi_char16_t *name) > > +{ > > + return ucs2_strsize(name, EFI_VAR_NAME_LEN) + 1; > > +} > > If this is really dynamic, I'm surprised that anything ends up > aligned. Can't this be a number like 6? It might pay to extend that > warning to also check that, if the variable is on the stack, its size > is a power of two. But maybe none of the users of this are on the > stack, in which case it might pay to try to prevent a new user on the > stack from showing up. I can't find any existing users that place strings on the stack, no. OK, let's try this one. --- >From 3f8a1ec209a458a9e4b82313186fbde86082696b 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 | 80 ++++++++++++++++++++++++++++++------------ 1 file changed, 57 insertions(+), 23 deletions(-) diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c index 58b0f801f66f..319148bd4b05 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 @@ -211,6 +212,35 @@ 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) +{ + bool bad_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. Try to catch strings on the stack by + * checking that 'size' is a power of two. + */ + bad_size = size > PAGE_SIZE || !is_power_of_2(size); + + WARN_ON(!IS_ALIGNED((unsigned long)va, size) || bad_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; @@ -494,8 +524,8 @@ 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 +541,7 @@ 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 +559,9 @@ 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 +579,7 @@ 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 +588,10 @@ 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 +601,11 @@ 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 +620,9 @@ 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 +639,9 @@ 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 +655,7 @@ 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 +667,7 @@ 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 +695,9 @@ 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