From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751092AbdADLj0 (ORCPT ); Wed, 4 Jan 2017 06:39:26 -0500 Received: from foss.arm.com ([217.140.101.70]:48880 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750837AbdADLjY (ORCPT ); Wed, 4 Jan 2017 06:39:24 -0500 From: Robin Murphy To: gregkh@linuxfoundation.org, Jason@zx2c4.com Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH] drivers: char: mem: Fix thinko in kmem address checks Date: Wed, 4 Jan 2017 11:37:49 +0000 Message-Id: <641a72e66f81d1244d8420074bc5def88d3929d4.1483529604.git.robin.murphy@arm.com> X-Mailer: git-send-email 2.10.2.dirty Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When borrowing the pfn_valid() check from mmap_kmem(), somebody managed 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) { -- 2.10.2.dirty