From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753219AbcFTHfR (ORCPT ); Mon, 20 Jun 2016 03:35:17 -0400 Received: from mail-wm0-f48.google.com ([74.125.82.48]:38619 "EHLO mail-wm0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751790AbcFTHfN (ORCPT ); Mon, 20 Jun 2016 03:35:13 -0400 From: Yigal Korman To: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, linux-kernel@vger.kernel.org Cc: linux-nvdimm@ml01.01.org, dan.j.williams@intel.com, elliott@hpe.com, jmoyer@redhat.com, toshi.kani@hpe.com, Yigal Korman Subject: [PATCH] x86/mm: only allow memmap=XX!YY over existing RAM Date: Mon, 20 Jun 2016 10:33:59 +0300 Message-Id: <1466408039-7497-1-git-send-email-yigal@plexistor.com> X-Mailer: git-send-email 1.9.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Before this patch, passing a range that is beyond the physical memory range will succeed, the user will see a /dev/pmem0 and will be able to access it. Reads will always return 0 and writes will be silently ignored. I've gotten more than one bug report about mkfs.{xfs,ext4} or nvml failing that were eventually tracked down to be wrong values passed to memmap. This patch prevents the above issue by instead of adding a new memory range, only update a RAM memory range with the PRAM type. This way, passing the wrong memmap will either not give you a pmem at all or give you a smaller one that actually has RAM behind it. And if someone still needs to fake a pmem that doesn't have RAM behind it, they can simply do memmap=XX@YY,XX!YY. Signed-off-by: Yigal Korman --- arch/x86/kernel/e820.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c index 621b501..4bd4207 100644 --- a/arch/x86/kernel/e820.c +++ b/arch/x86/kernel/e820.c @@ -878,7 +878,7 @@ static int __init parse_memmap_one(char *p) e820_add_region(start_at, mem_size, E820_RESERVED); } else if (*p == '!') { start_at = memparse(p+1, &p); - e820_add_region(start_at, mem_size, E820_PRAM); + e820_update_range(start_at, mem_size, E820_RAM, E820_PRAM); } else e820_remove_range(mem_size, ULLONG_MAX - mem_size, E820_RAM, 1); -- 1.9.3