From patchwork Sun Jun 12 21:32:27 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Wilcox X-Patchwork-Id: 12878847 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C5F91CCA473 for ; Sun, 12 Jun 2022 21:32:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236182AbiFLVcp (ORCPT ); Sun, 12 Jun 2022 17:32:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50162 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235950AbiFLVcn (ORCPT ); Sun, 12 Jun 2022 17:32:43 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4692D9FE8; Sun, 12 Jun 2022 14:32:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Transfer-Encoding:MIME-Version: References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Sender:Reply-To: Content-Type:Content-ID:Content-Description; bh=HTrppkgyoE0jfkD/I3hwHGO9wel7JMRK5JWmxra0aTw=; b=SEdm11PHMGs3xIT5eFgs1AaLQw wBdGhsxowR+3VG3Z0qlqYVd4ShqfwhcvCeXebJDQgFdY21nGO8jGU1DiQ9AnXML62aXC9T9iJ+xqE ZaQFMUEEbXRdl1IMHc60ASgvvamq7MuPHSP1mYdaxzNfDsL6pe3370ki95kajTAbs4E9G8M7XpSva qayDemMjdO4a79683xTqgJLYpn/2Q+rd2YonUuDU7DgtZ7ppIissSTdoJs4IUW+zX/+2vkE+ezHUC tJjdE39HiA2gssJMq9StqsbNVvNpaQY/pdSNrHJbus6q0krzIq7U/nYgXzmP4Q3fh+G+ICbIlUBSl lFYersDQ==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1o0VC9-00GHq0-GJ; Sun, 12 Jun 2022 21:32:29 +0000 From: "Matthew Wilcox (Oracle)" To: Kees Cook Cc: "Matthew Wilcox (Oracle)" , linux-mm@kvack.org, Uladzislau Rezki , Zorro Lang , linux-xfs@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH 3/3] usercopy: Make usercopy resilient against ridiculously large copies Date: Sun, 12 Jun 2022 22:32:27 +0100 Message-Id: <20220612213227.3881769-4-willy@infradead.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20220612213227.3881769-1-willy@infradead.org> References: <20220612213227.3881769-1-willy@infradead.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org If 'n' is so large that it's negative, we might wrap around and mistakenly think that the copy is OK when it's not. Such a copy would probably crash, but just doing the arithmetic in a more simple way lets us detect and refuse this case. Signed-off-by: Matthew Wilcox (Oracle) --- mm/usercopy.c | 19 +++++++++---------- 1 file changed, 9 insertions(+), 10 deletions(-) diff --git a/mm/usercopy.c b/mm/usercopy.c index 31deee7dd2f5..ff16083cf1c8 100644 --- a/mm/usercopy.c +++ b/mm/usercopy.c @@ -162,20 +162,18 @@ static inline void check_heap_object(const void *ptr, unsigned long n, bool to_user) { uintptr_t addr = (uintptr_t)ptr; + unsigned long offset; struct folio *folio; if (is_kmap_addr(ptr)) { - unsigned long page_end = addr | (PAGE_SIZE - 1); - - if (addr + n - 1 > page_end) - usercopy_abort("kmap", NULL, to_user, - offset_in_page(ptr), n); + offset = offset_in_page(ptr); + if (n > PAGE_SIZE - offset) + usercopy_abort("kmap", NULL, to_user, offset, n); return; } if (is_vmalloc_addr(ptr)) { struct vmap_area *area = find_vmap_area(addr); - unsigned long offset; if (!area) { usercopy_abort("vmalloc", "no area", to_user, 0, n); @@ -184,9 +182,10 @@ static inline void check_heap_object(const void *ptr, unsigned long n, /* XXX: We should also abort for free vmap_areas */ - offset = addr - area->va_start; - if (addr + n > area->va_end) + if (n > area->va_end - addr) { + offset = addr - area->va_start; usercopy_abort("vmalloc", NULL, to_user, offset, n); + } return; } @@ -199,8 +198,8 @@ static inline void check_heap_object(const void *ptr, unsigned long n, /* Check slab allocator for flags and size. */ __check_heap_object(ptr, n, folio_slab(folio), to_user); } else if (folio_test_large(folio)) { - unsigned long offset = ptr - folio_address(folio); - if (offset + n > folio_size(folio)) + offset = ptr - folio_address(folio); + if (n > folio_size(folio) - offset) usercopy_abort("page alloc", NULL, to_user, offset, n); } }