From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AG47ELuSvKu7oFOG7RRpRsiv+7IhvdI6dPSeGmVQ/tHVW555zV9+1SDxfTDOAbiPZPW7ulHSYYkv ARC-Seal: i=1; a=rsa-sha256; t=1520824083; cv=none; d=google.com; s=arc-20160816; b=oNgMWskRFqM+nQ5UOHHRpj8ReGHcp9V+r+jwSb4eX2mQNz9yBKaieRkK+LgqD3M9N1 DknQcHxnHTZ3p+Pvrsyk/SJfM/q+2zRoYGWYxLANJNNwxZ9Vm9sCVmleLyG2THbHaovV IpyLbYcYrGrxsFSYWaVaXbx0qTPPcqPjTDAEp3NFVqcxOtan+gGFgoj5GA+l9G/5zs/F 4LxFUpt2Smaw4qc+MyzB2wgidiQEDraB+d4AybI8LByBxcMaV0U1bKZ+ykhZP6tFoQgH t3T6GdGtF0OQcqdAo6zwSPEhJ11Y3W1CTE7yqK/bNx8G8E513flr1LGjDDMXOJ0UnkGu lYoA== 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=wSD8m/d9LC1y4yw3+hWBMVUDcD4oEy/MIrG03fagOms=; b=ovkD7IV7RkE0JoJyU/hB/WlSuIrmrhTGOnRnUen4iyBo8xREFpVfWnduSIr55Li0ku RjVgCR/wXM4lyYK3Dgdvn+EXqPYtwNvwstxZFy01g5oQlJ/pOIfQpNxnIdI4yU7hp2s2 tNOjdotuqLpLTWQkNwEqwviUHQYQZso1xVuPDXhXJHw/TCNBl6kHu4Jkof9Y9aXVxz0/ /nFfjwXvTcEmpkFQ3zPJ2Jf9OY4nqV2dorjES1SEbkF5T8EkR2m0JvOq7zsmO7E6l/g0 Jazw42x0dhgtS3Sji62UFMh3eZ8XlY+BO4wiSxOndk6nMj0eFZBphlBFSJZ5TyvZT+dl EfFw== 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, "Dave Hansen" , "Thomas Gleixner" , "Greg Kroah-Hartman" , "Jiri Kosina" , "Borislav Petkov" , "Andi Kleen" , "Tom Lendacky" , "Linus Torvalds" , "Paul Turner" , "David Woodhouse" , "Tim Chen" , "Andrew Lutomirski" , "Peter Zijlstra" , "Andi Kleen" Date: Mon, 12 Mar 2018 03:03:34 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 052/104] 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?1594699633715213598?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 3.2.101-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 @@ -324,9 +324,12 @@ 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);