From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752013AbdADLq5 (ORCPT ); Wed, 4 Jan 2017 06:46:57 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:40676 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751384AbdADLql (ORCPT ); Wed, 4 Jan 2017 06:46:41 -0500 Date: Wed, 4 Jan 2017 12:45:32 +0100 From: Greg KH To: Robin Murphy Cc: Jason@zx2c4.com, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] drivers: char: mem: Fix thinko in kmem address checks Message-ID: <20170104114532.GA6449@kroah.com> References: <641a72e66f81d1244d8420074bc5def88d3929d4.1483529604.git.robin.murphy@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <641a72e66f81d1244d8420074bc5def88d3929d4.1483529604.git.robin.murphy@arm.com> User-Agent: Mutt/1.7.2 (2016-11-26) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 04, 2017 at 11:37:49AM +0000, Robin Murphy wrote: > When borrowing the pfn_valid() check from mmap_kmem(), somebody managed "sombody"? :) > to get physical and virtual addresses spectacularly muddled up, such > that we've ended up with checks for one being the other. Whilst this > does indeed prevent out-of-bounds accesses crashing, on most systems it > also prevents the more desirable use-case of working at all ever. > > Check the *virtual* offset correctly for what it is. > > Reported-by: Jason A. Donenfeld > CC: stable@vger.kernel.org > Fixes: 148a1bc84398 ("drivers: char: mem: Check {read,write}_kmem() addresses") > Signed-off-by: Robin Murphy > --- > drivers/char/mem.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/char/mem.c b/drivers/char/mem.c > index 5bb1985ec484..bdc6a4018604 100644 > --- a/drivers/char/mem.c > +++ b/drivers/char/mem.c > @@ -381,7 +381,7 @@ static ssize_t read_kmem(struct file *file, char __user *buf, > char *kbuf; /* k-addr because vread() takes vmlist_lock rwlock */ > int err = 0; > > - if (!pfn_valid(PFN_DOWN(p))) > + if (!virt_addr_valid(p)) > return -EIO; > > read = 0; > @@ -512,7 +512,7 @@ static ssize_t write_kmem(struct file *file, const char __user *buf, > char *kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */ > int err = 0; > > - if (!pfn_valid(PFN_DOWN(p))) > + if (!virt_addr_valid(p)) > return -EIO; > > if (p < (unsigned long) high_memory) { Jason, can you verify this fixes your test case? thanks, greg k-h