Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753705AbaFEEjA (ORCPT ); Thu, 5 Jun 2014 00:39:00 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:44297 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753264AbaFEEVp (ORCPT ); Thu, 5 Jun 2014 00:21:45 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Matthew Garrett , Matt Fleming , Ben Hutchings , Rui Xiang , "Lee, Chun-Y" Subject: [PATCH 3.4 154/214] Modify UEFI anti-bricking code Date: Wed, 4 Jun 2014 21:18:37 -0700 Message-Id: <20140605041700.428456416@linuxfoundation.org> X-Mailer: git-send-email 2.0.0 In-Reply-To: <20140605041639.638675216@linuxfoundation.org> References: <20140605041639.638675216@linuxfoundation.org> User-Agent: quilt/0.60-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Matthew Garrett commit f8b8404337de4e2466e2e1139ea68b1f8295974f upstream. This patch reworks the UEFI anti-bricking code, including an effective reversion of cc5a080c and 31ff2f20. It turns out that calling QueryVariableInfo() from boot services results in some firmware implementations jumping to physical addresses even after entering virtual mode, so until we have 1:1 mappings for UEFI runtime space this isn't going to work so well. Reverting these gets us back to the situation where we'd refuse to create variables on some systems because they classify deleted variables as "used" until the firmware triggers a garbage collection run, which they won't do until they reach a lower threshold. This results in it being impossible to install a bootloader, which is unhelpful. Feedback from Samsung indicates that the firmware doesn't need more than 5KB of storage space for its own purposes, so that seems like a reasonable threshold. However, there's still no guarantee that a platform will attempt garbage collection merely because it drops below this threshold. It seems that this is often only triggered if an attempt to write generates a genuine EFI_OUT_OF_RESOURCES error. We can force that by attempting to create a variable larger than the remaining space. This should fail, but if it somehow succeeds we can then immediately delete it. I've tested this on the UEFI machines I have available, but I don't have a Samsung and so can't verify that it avoids the bricking problem. Signed-off-by: Matthew Garrett Signed-off-by: Lee, Chun-Y [ dummy variable cleanup ] Signed-off-by: Matt Fleming [bwh: Backported to 3.2: the reverted changes were never applied here] Signed-off-by: Ben Hutchings Cc: Rui Xiang Signed-off-by: Greg Kroah-Hartman --- arch/x86/platform/efi/efi.c | 79 +++++++++++++++++++++++++++++++++++++------- 1 file changed, 68 insertions(+), 11 deletions(-) --- a/arch/x86/platform/efi/efi.c +++ b/arch/x86/platform/efi/efi.c @@ -50,6 +50,13 @@ #define EFI_DEBUG 1 +#define EFI_MIN_RESERVE 5120 + +#define EFI_DUMMY_GUID \ + EFI_GUID(0x4424ac57, 0xbe4b, 0x47dd, 0x9e, 0x97, 0xed, 0x50, 0xf0, 0x9f, 0x92, 0xa9) + +static efi_char16_t efi_dummy_name[6] = { 'D', 'U', 'M', 'M', 'Y', 0 }; + struct efi __read_mostly efi = { .mps = EFI_INVALID_TABLE_ADDR, .acpi = EFI_INVALID_TABLE_ADDR, @@ -932,6 +939,13 @@ void __init efi_enter_virtual_mode(void) runtime_code_page_mkexec(); kfree(new_memmap); + + /* clean DUMMY object */ + efi.set_variable(efi_dummy_name, &EFI_DUMMY_GUID, + EFI_VARIABLE_NON_VOLATILE | + EFI_VARIABLE_BOOTSERVICE_ACCESS | + EFI_VARIABLE_RUNTIME_ACCESS, + 0, NULL); } /* @@ -983,22 +997,65 @@ efi_status_t efi_query_variable_store(u3 efi_status_t status; u64 storage_size, remaining_size, max_size; + if (!(attributes & EFI_VARIABLE_NON_VOLATILE)) + return 0; + status = efi.query_variable_info(attributes, &storage_size, &remaining_size, &max_size); if (status != EFI_SUCCESS) return status; - if (!max_size && remaining_size > size) - printk_once(KERN_ERR FW_BUG "Broken EFI implementation" - " is returning MaxVariableSize=0\n"); - - if (!storage_size || size > remaining_size || - (max_size && size > max_size)) - return EFI_OUT_OF_RESOURCES; - - if (!efi_no_storage_paranoia && - (remaining_size - size) < (storage_size / 2)) - return EFI_OUT_OF_RESOURCES; + /* + * Some firmware implementations refuse to boot if there's insufficient + * space in the variable store. We account for that by refusing the + * write if permitting it would reduce the available space to under + * 5KB. This figure was provided by Samsung, so should be safe. + */ + if ((remaining_size - size < EFI_MIN_RESERVE) && + !efi_no_storage_paranoia) { + + /* + * Triggering garbage collection may require that the firmware + * generate a real EFI_OUT_OF_RESOURCES error. We can force + * that by attempting to use more space than is available. + */ + unsigned long dummy_size = remaining_size + 1024; + void *dummy = kmalloc(dummy_size, GFP_ATOMIC); + + status = efi.set_variable(efi_dummy_name, &EFI_DUMMY_GUID, + EFI_VARIABLE_NON_VOLATILE | + EFI_VARIABLE_BOOTSERVICE_ACCESS | + EFI_VARIABLE_RUNTIME_ACCESS, + dummy_size, dummy); + + if (status == EFI_SUCCESS) { + /* + * This should have failed, so if it didn't make sure + * that we delete it... + */ + efi.set_variable(efi_dummy_name, &EFI_DUMMY_GUID, + EFI_VARIABLE_NON_VOLATILE | + EFI_VARIABLE_BOOTSERVICE_ACCESS | + EFI_VARIABLE_RUNTIME_ACCESS, + 0, dummy); + } + + /* + * The runtime code may now have triggered a garbage collection + * run, so check the variable info again + */ + status = efi.query_variable_info(attributes, &storage_size, + &remaining_size, &max_size); + + if (status != EFI_SUCCESS) + return status; + + /* + * There still isn't enough room, so return an error + */ + if (remaining_size - size < EFI_MIN_RESERVE) + return EFI_OUT_OF_RESOURCES; + } return EFI_SUCCESS; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/