From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757483AbcGZWqJ (ORCPT ); Tue, 26 Jul 2016 18:46:09 -0400 Received: from relay2.sgi.com ([192.48.180.65]:57001 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751453AbcGZWqG (ORCPT ); Tue, 26 Jul 2016 18:46:06 -0400 X-Greylist: delayed 450 seconds by postgrey-1.27 at vger.kernel.org; Tue, 26 Jul 2016 18:46:06 EDT From: Alex Thorlton To: linux-kernel@vger.kernel.org Cc: Alex Thorlton , Russ Anderson , Mike Travis , Matt Fleming , Borislav Petkov , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org Subject: [PATCH] Skip UV runtime services mapping in the efi_runtime_disabled case Date: Tue, 26 Jul 2016 17:38:33 -0500 Message-Id: <1469572713-113354-2-git-send-email-athorlton@sgi.com> X-Mailer: git-send-email 1.8.5.6 In-Reply-To: <1469572713-113354-1-git-send-email-athorlton@sgi.com> References: <1469572713-113354-1-git-send-email-athorlton@sgi.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This problem has actually been in the UV code for a while, but we didn't catch it until recently, because we had been relying on EFI_OLD_MEMMAP to allow our systems to boot for a period of time. We noticed the issue when trying to kexec a recent community kernel, where we hit this NULL pointer dereference in efi_sync_low_kernel_mappings: [ 0.337515] BUG: unable to handle kernel NULL pointer dereference at 0000000000000880 [ 0.346276] IP: [] efi_sync_low_kernel_mappings+0x5d/0x1b0 The problem doesn't show up with EFI_OLD_MEMMAP because we skip the chunk of setup_efi_state that sets the efi_loader_signature for the kexec'd kernel. When the kexec'd kernel boots, it won't set EFI_BOOT in setup_arch, so we completely avoid the bug. We always kexec with noefi on the command line, so this shouldn't be an issue, but since we're not actually checking for efi_runtime_disabled in uv_bios_init, we end up trying to do EFI runtime callbacks when we shouldn't be. This patch just adds a check for efi_runtime_disabled in uv_bios_init so that we don't map in uv_systab when runtime_disabled == true. Signed-off-by: Alex Thorlton Cc: Russ Anderson Cc: Mike Travis Cc: Matt Fleming Cc: Borislav Petkov Cc: Thomas Gleixner Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: x86@kernel.org --- arch/x86/platform/uv/bios_uv.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/platform/uv/bios_uv.c b/arch/x86/platform/uv/bios_uv.c index 66b2166..0df8a03 100644 --- a/arch/x86/platform/uv/bios_uv.c +++ b/arch/x86/platform/uv/bios_uv.c @@ -187,7 +187,8 @@ EXPORT_SYMBOL_GPL(uv_bios_set_legacy_vga_target); void uv_bios_init(void) { uv_systab = NULL; - if ((efi.uv_systab == EFI_INVALID_TABLE_ADDR) || !efi.uv_systab) { + if ((efi.uv_systab == EFI_INVALID_TABLE_ADDR) || + !efi.uv_systab || efi_runtime_disabled()) { pr_crit("UV: UVsystab: missing\n"); return; } -- 1.8.5.6