From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9B12CC2BA17 for ; Mon, 6 Apr 2020 16:41:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6C8342496D for ; Mon, 6 Apr 2020 16:41:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="I6aOOb4F" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729649AbgDFQl4 (ORCPT ); Mon, 6 Apr 2020 12:41:56 -0400 Received: from mail-vs1-f73.google.com ([209.85.217.73]:40109 "EHLO mail-vs1-f73.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729529AbgDFQly (ORCPT ); Mon, 6 Apr 2020 12:41:54 -0400 Received: by mail-vs1-f73.google.com with SMTP id w2so9975vsf.7 for ; Mon, 06 Apr 2020 09:41:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=P7tRJ6/bRwi2I74AEfEJ7NL6sovvq6Ksezb3luMLZ/I=; b=I6aOOb4F+m585U3+RTjXCgdA35wkhP1CN3Uhmh+0KXvkwJcQQrkknIVKYFc21EGa9T gXREpmuKmKvxZJQyHbkni+ojnnrEUvsfKtX9CGOGZlTJmkKexDQDF2et3kSeqToQRiKo Wt+3R+N5GtS2ABYhkNEB3tNvZvXgtf9rP6ZYtHP7qsABnpKM8zORokraX7ZOWpN6zase 7NeHFG/CLonjoUheDOHlw7LzXo3Z6KjdaB9CNgPtQJRi3+pdaP4ZaWGXm8Emnc+boObD Up/eCuQFeygzhdH7a2SHIC/Eb6fhV//t/0cYReB1Mak0oksza68jY0Bqyf5hZJG0QQMh gQVA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=P7tRJ6/bRwi2I74AEfEJ7NL6sovvq6Ksezb3luMLZ/I=; b=mxM4jVWc/SacG4CewmwmkTzsXrHLt9ZkPOE1trNOd0XVS/oL3w49Od9I5lCHOV9GE4 kKA2tY2iMKta8atVs/COFLgPXl2LrdYaljuyHXqQPsgAEVtWJX/5P5EbIi64PzUZkwTj BtPCpY6BuouC/Ac0Rr39n54jIH/o2A2zgEu8nNIR30nDh5IIYIN0eJe6ad5UCLhPI6on V+ON/3qVYs+vi4pvI4VkzQucI3NwuVYeY81WwHxHQ4Bxhaw4Tl4zaqcI1tWTvP8RjKBB jtPP0bVd78nK10O8yljayVbsnwXItuCKW43xY7Xxv9+blGu+OPhOTHNkczXH0LsB6CDW Da1A== X-Gm-Message-State: AGi0PubkhYC1f+rtr+I3O0Ff8C9gnyNffMRlcSMYc9Rkty7QLMDX/zpT Z7lK3W2LYvl+sgzr/dic/FErxVG6KHcVHRqxcBM= X-Google-Smtp-Source: APiQypJJ2vW2BCKCiSZ+xIRCi6v70yfbRRHeakQcdO++WZV928etab2mQBvVqnKPYnI22hBzW364z/buE5ZaeQqgJWo= X-Received: by 2002:a67:fb0f:: with SMTP id d15mr471360vsr.88.1586191313260; Mon, 06 Apr 2020 09:41:53 -0700 (PDT) Date: Mon, 6 Apr 2020 09:41:16 -0700 In-Reply-To: <20200406164121.154322-1-samitolvanen@google.com> Message-Id: <20200406164121.154322-8-samitolvanen@google.com> Mime-Version: 1.0 References: <20191018161033.261971-1-samitolvanen@google.com> <20200406164121.154322-1-samitolvanen@google.com> X-Mailer: git-send-email 2.26.0.292.g33ef6b2f38-goog Subject: [PATCH v10 07/12] arm64: efi: restore x18 if it was corrupted From: Sami Tolvanen To: Will Deacon , Catalin Marinas , James Morse , Steven Rostedt , Masami Hiramatsu , Ard Biesheuvel , Mark Rutland Cc: Dave Martin , Kees Cook , Laura Abbott , Marc Zyngier , Nick Desaulniers , Jann Horn , Miguel Ojeda , Masahiro Yamada , clang-built-linux@googlegroups.com, kernel-hardening@lists.openwall.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Sami Tolvanen Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If we detect a corrupted x18, restore the register before jumping back to potentially SCS instrumented code. This is safe, because the wrapper is called with preemption disabled and a separate shadow stack is used for interrupt handling. Signed-off-by: Sami Tolvanen Reviewed-by: Kees Cook Acked-by: Will Deacon --- arch/arm64/kernel/efi-rt-wrapper.S | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kernel/efi-rt-wrapper.S b/arch/arm64/kernel/efi-rt-wrapper.S index 3fc71106cb2b..6ca6c0dc11a1 100644 --- a/arch/arm64/kernel/efi-rt-wrapper.S +++ b/arch/arm64/kernel/efi-rt-wrapper.S @@ -34,5 +34,14 @@ ENTRY(__efi_rt_asm_wrapper) ldp x29, x30, [sp], #32 b.ne 0f ret -0: b efi_handle_corrupted_x18 // tail call +0: + /* + * With CONFIG_SHADOW_CALL_STACK, the kernel uses x18 to store a + * shadow stack pointer, which we need to restore before returning to + * potentially instrumented code. This is safe because the wrapper is + * called with preemption disabled and a separate shadow stack is used + * for interrupts. + */ + mov x18, x2 + b efi_handle_corrupted_x18 // tail call ENDPROC(__efi_rt_asm_wrapper) -- 2.26.0.292.g33ef6b2f38-goog