From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ot0-f200.google.com (mail-ot0-f200.google.com [74.125.82.200]) by kanga.kvack.org (Postfix) with ESMTP id 9B4486B0003 for ; Tue, 1 May 2018 16:11:53 -0400 (EDT) Received: by mail-ot0-f200.google.com with SMTP id 37-v6so9851240otv.2 for ; Tue, 01 May 2018 13:11:53 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id 84-v6sor4612058oik.277.2018.05.01.13.11.52 for (Google Transport Security); Tue, 01 May 2018 13:11:52 -0700 (PDT) From: Laura Abbott Subject: [PATCH] proc/kcore: Don't bounds check against address 0 Date: Tue, 1 May 2018 13:11:43 -0700 Message-Id: <20180501201143.15121-1-labbott@redhat.com> In-Reply-To: <1039518799.26129578.1525185916272.JavaMail.zimbra@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: Dave Anderson , Kees Cook , akpm@linux-foundation.org Cc: Laura Abbott , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, Ard Biesheuvel , Ingo Molnar , Andi Kleen The existing kcore code checks for bad addresses against __va(0) with the assumption that this is the lowest address on the system. This may not hold true on some systems (e.g. arm64) and produce overflows and crashes. Switch to using other functions to validate the address range. Tested-by: Dave Anderson Signed-off-by: Laura Abbott --- I took your previous comments as a tested by, please let me know if that was wrong. This should probably just go through -mm. I don't think this is necessary for stable but I can request it later if necessary. --- fs/proc/kcore.c | 23 ++++++++++++++++------- 1 file changed, 16 insertions(+), 7 deletions(-) diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c index d1e82761de81..e64ecb9f2720 100644 --- a/fs/proc/kcore.c +++ b/fs/proc/kcore.c @@ -209,25 +209,34 @@ kclist_add_private(unsigned long pfn, unsigned long nr_pages, void *arg) { struct list_head *head = (struct list_head *)arg; struct kcore_list *ent; + struct page *p; + + if (!pfn_valid(pfn)) + return 1; + + p = pfn_to_page(pfn); + if (!memmap_valid_within(pfn, p, page_zone(p))) + return 1; ent = kmalloc(sizeof(*ent), GFP_KERNEL); if (!ent) return -ENOMEM; - ent->addr = (unsigned long)__va((pfn << PAGE_SHIFT)); + ent->addr = (unsigned long)page_to_virt(p); ent->size = nr_pages << PAGE_SHIFT; - /* Sanity check: Can happen in 32bit arch...maybe */ - if (ent->addr < (unsigned long) __va(0)) + if (!virt_addr_valid(ent->addr)) goto free_out; /* cut not-mapped area. ....from ppc-32 code. */ if (ULONG_MAX - ent->addr < ent->size) ent->size = ULONG_MAX - ent->addr; - /* cut when vmalloc() area is higher than direct-map area */ - if (VMALLOC_START > (unsigned long)__va(0)) { - if (ent->addr > VMALLOC_START) - goto free_out; + /* + * We've already checked virt_addr_valid so we know this address + * is a valid pointer, therefore we can check against it to determine + * if we need to trim + */ + if (VMALLOC_START > ent->addr) { if (VMALLOC_START - ent->addr < ent->size) ent->size = VMALLOC_START - ent->addr; } -- 2.14.3