From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AG47ELsQnC/5KODaAGQhbvYvY5oNvyzWznoTvwaqeoRaprLCPzaUaCuaXMQUh0ekYLsolXJtHD4O ARC-Seal: i=1; a=rsa-sha256; t=1520824085; cv=none; d=google.com; s=arc-20160816; b=gHqURC8XHlSZH/Ve75IV3lA2uCfGpnRllufBwhneYUXavgw6uXUzijlqmjY+xGJK36 tNuvDZfJziTVytnGBoLYG9wtpWGjM3jxTDVIiyDnXB3x1LMiLFktS4tkpn1+xAt+7qXe 8m+/fd/9OpqBnUwBTji2wovr7Hty59TDMhmk7OYlnKEpPuN/7whe6Sk7h76/iciVReTp TD7l2eWoPTw8pdVMtAMcC7urYixn5Ur6OVP5+nqBT4a+f1/sv+zDTyFjQSp8BLnkVKsp Y50n5ICLHUEOOkxSXcUCXeQtGvJvqHV2RGXU6INWm+EbleyMWsKaCeCzKgZg5lE2YW45 Yclg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=in-reply-to:subject:message-id:date:cc:to:from:mime-version :content-transfer-encoding:content-disposition :arc-authentication-results; bh=qPD1gtJlrp2HEVedFTyvP+pScuy+a6PY6cUffllHPkU=; b=YIgqlMtFyYh651xTr/Dfw0tUe0JfO6YqA9Jc4SUMKSzTpxR51DBw6xEcwqUEuzpbrP 5/TcLB5dIidz3AXU+kHiO3hkGrLhGi+NaDLxuqUxxvCgyeV11ZQs8pZQXQvWQAsmCU4D hnSEbu9nYcck2rFryqlc0LkWpjZcNnjsdNfhB2FaMaDOO0qWiAnK/cWxsZIeSaY1uWGz Cf3SfWK4wnpt2/axOIUQksCBgZEYgkD9sk2X/HzPH3uVa8U1Hmxy5w5x2RzswIj1GnOv 7D4SbbGcZbXG6u7TOaWD2GwZlM5x1mlWHw39FMlx8oH1+ZoMJmUwdM3rHeEsSzVihX7x xazg== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of ben@decadent.org.uk designates 88.96.1.126 as permitted sender) smtp.mailfrom=ben@decadent.org.uk Authentication-Results: mx.google.com; spf=pass (google.com: domain of ben@decadent.org.uk designates 88.96.1.126 as permitted sender) smtp.mailfrom=ben@decadent.org.uk Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Linus Torvalds" , "Paul Turner" , "Borislav Petkov" , "Andi Kleen" , "Tim Chen" , "Andrew Lutomirski" , "David Woodhouse" , "Andi Kleen" , "Peter Zijlstra" , "Thomas Gleixner" , "Greg Kroah-Hartman" , "Tom Lendacky" , "Jiri Kosina" , "Dave Hansen" Date: Mon, 12 Mar 2018 03:06:12 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 16/76] x86/alternatives: Fix optimize_nops() checking In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1594699636412875983?= X-GMAIL-MSGID: =?utf-8?q?1594699636412875983?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 3.16.56-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Borislav Petkov commit 612e8e9350fd19cae6900cf36ea0c6892d1a0dca upstream. The alternatives code checks only the first byte whether it is a NOP, but with NOPs in front of the payload and having actual instructions after it breaks the "optimized' test. Make sure to scan all bytes before deciding to optimize the NOPs in there. Reported-by: David Woodhouse Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Cc: Tom Lendacky Cc: Andi Kleen Cc: Tim Chen Cc: Peter Zijlstra Cc: Jiri Kosina Cc: Dave Hansen Cc: Andi Kleen Cc: Andrew Lutomirski Cc: Linus Torvalds Cc: Greg Kroah-Hartman Cc: Paul Turner Link: https://lkml.kernel.org/r/20180110112815.mgciyf5acwacphkq@pd.tnic Signed-off-by: Ben Hutchings --- arch/x86/kernel/alternative.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -326,9 +326,12 @@ done: static void __init_or_module optimize_nops(struct alt_instr *a, u8 *instr) { unsigned long flags; + int i; - if (instr[0] != 0x90) - return; + for (i = 0; i < a->padlen; i++) { + if (instr[i] != 0x90) + return; + } local_irq_save(flags); add_nops(instr + (a->instrlen - a->padlen), a->padlen);