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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 90442C433EF for ; Fri, 22 Jul 2022 09:23:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235857AbiGVJXY (ORCPT ); Fri, 22 Jul 2022 05:23:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35198 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236219AbiGVJXA (ORCPT ); Fri, 22 Jul 2022 05:23:00 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0A12AC0B5A; Fri, 22 Jul 2022 02:14:48 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 0AFD1B827BE; Fri, 22 Jul 2022 09:14:47 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 545AAC341C6; Fri, 22 Jul 2022 09:14:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1658481285; bh=Sp4lzYf28TvH726a0QxviKjDpHbCkEZsCj2pLcovfbc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=djAu6YFb2Ow+mgEnherdbvf400jatDcQkuRTKHBKBjjLsL0nbBn97hI6mbOS3045a kgElRJ7N+GFeqcPzCXwGmqoXpWPhYW0AdBfVzNfNKMywplbl9Csp8uH9cpr+JffbXO FYkl4k4URoaQmeyPnnq+89scJKHh9J9mXEIKhm0g= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Peter Zijlstra (Intel)" , Borislav Petkov , Josh Poimboeuf , Thadeu Lima de Souza Cascardo Subject: [PATCH 5.15 39/89] x86/entry: Avoid very early RET Date: Fri, 22 Jul 2022 11:11:13 +0200 Message-Id: <20220722091135.548369561@linuxfoundation.org> X-Mailer: git-send-email 2.37.1 In-Reply-To: <20220722091133.320803732@linuxfoundation.org> References: <20220722091133.320803732@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peter Zijlstra commit 7c81c0c9210c9bfab2bae76aab2999de5bad27db upstream. Commit ee774dac0da1 ("x86/entry: Move PUSH_AND_CLEAR_REGS out of error_entry()") manages to introduce a CALL/RET pair that is before SWITCH_TO_KERNEL_CR3, which means it is before RETBleed can be mitigated. Revert to an earlier version of the commit in Fixes. Down side is that this will bloat .text size somewhat. The alternative is fully reverting it. The purpose of this patch was to allow migrating error_entry() to C, including the whole of kPTI. Much care needs to be taken moving that forward to not re-introduce this problem of early RETs. Fixes: ee774dac0da1 ("x86/entry: Move PUSH_AND_CLEAR_REGS out of error_entry()") Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov Reviewed-by: Josh Poimboeuf Signed-off-by: Borislav Petkov Signed-off-by: Thadeu Lima de Souza Cascardo Signed-off-by: Greg Kroah-Hartman --- arch/x86/entry/entry_64.S | 12 ++---------- 1 file changed, 2 insertions(+), 10 deletions(-) --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -314,14 +314,6 @@ SYM_CODE_END(ret_from_fork) #endif .endm -/* Save all registers in pt_regs */ -SYM_CODE_START_LOCAL(push_and_clear_regs) - UNWIND_HINT_FUNC - PUSH_AND_CLEAR_REGS save_ret=1 - ENCODE_FRAME_POINTER 8 - RET -SYM_CODE_END(push_and_clear_regs) - /** * idtentry_body - Macro to emit code calling the C function * @cfunc: C function to be called @@ -329,8 +321,8 @@ SYM_CODE_END(push_and_clear_regs) */ .macro idtentry_body cfunc has_error_code:req - call push_and_clear_regs - UNWIND_HINT_REGS + PUSH_AND_CLEAR_REGS + ENCODE_FRAME_POINTER /* * Call error_entry() and switch to the task stack if from userspace.