From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:37292 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933867AbeAKOWz (ORCPT ); Thu, 11 Jan 2018 09:22:55 -0500 Subject: Patch "x86/mm/pat, /dev/mem: Remove superfluous error message" has been added to the 4.4-stable tree To: jkosina@suse.cz, akpm@linux-foundation.org, bp@alien8.de, brgerst@gmail.com, dvlasenk@redhat.com, gregkh@linuxfoundation.org, hpa@zytor.com, jpoimboe@redhat.com, keescook@chromium.org, luto@kernel.org, mcgrof@suse.com, mingo@kernel.org, peterz@infradead.org, tglx@linutronix.de, torvalds@linux-foundation.org, toshi.kani@hp.com Cc: , From: Date: Thu, 11 Jan 2018 15:22:25 +0100 Message-ID: <1515680545198197@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled x86/mm/pat, /dev/mem: Remove superfluous error message to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: x86-mm-pat-dev-mem-remove-superfluous-error-message.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 39380b80d72723282f0ea1d1bbf2294eae45013e Mon Sep 17 00:00:00 2001 From: Jiri Kosina Date: Fri, 8 Jul 2016 11:38:28 +0200 Subject: x86/mm/pat, /dev/mem: Remove superfluous error message From: Jiri Kosina commit 39380b80d72723282f0ea1d1bbf2294eae45013e upstream. Currently it's possible for broken (or malicious) userspace to flood a kernel log indefinitely with messages a-la Program dmidecode tried to access /dev/mem between f0000->100000 because range_is_allowed() is case of CONFIG_STRICT_DEVMEM being turned on dumps this information each and every time devmem_is_allowed() fails. Reportedly userspace that is able to trigger contignuous flow of these messages exists. It would be possible to rate limit this message, but that'd have a questionable value; the administrator wouldn't get information about all the failing accessess, so then the information would be both superfluous and incomplete at the same time :) Returning EPERM (which is what is actually happening) is enough indication for userspace what has happened; no need to log this particular error as some sort of special condition. Signed-off-by: Jiri Kosina Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Kees Cook Cc: Linus Torvalds Cc: Luis R. Rodriguez Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Toshi Kani Link: http://lkml.kernel.org/r/alpine.LNX.2.00.1607081137020.24757@cbobk.fhfr.pm Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- arch/x86/mm/pat.c | 5 +---- drivers/char/mem.c | 6 +----- 2 files changed, 2 insertions(+), 9 deletions(-) --- a/arch/x86/mm/pat.c +++ b/arch/x86/mm/pat.c @@ -750,11 +750,8 @@ static inline int range_is_allowed(unsig return 1; while (cursor < to) { - if (!devmem_is_allowed(pfn)) { - pr_info("x86/PAT: Program %s tried to access /dev/mem between [mem %#010Lx-%#010Lx], PAT prevents it\n", - current->comm, from, to - 1); + if (!devmem_is_allowed(pfn)) return 0; - } cursor += PAGE_SIZE; pfn++; } --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -70,12 +70,8 @@ static inline int range_is_allowed(unsig u64 cursor = from; while (cursor < to) { - if (!devmem_is_allowed(pfn)) { - printk(KERN_INFO - "Program %s tried to access /dev/mem between %Lx->%Lx.\n", - current->comm, from, to); + if (!devmem_is_allowed(pfn)) return 0; - } cursor += PAGE_SIZE; pfn++; } Patches currently in stable-queue which might be from jkosina@suse.cz are queue-4.4/x86-mm-pat-dev-mem-remove-superfluous-error-message.patch