From patchwork Thu Dec 16 21:53:51 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Wilcox X-Patchwork-Id: 12682807 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 5A2C2C433EF for ; Thu, 16 Dec 2021 21:53:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235255AbhLPVx5 (ORCPT ); Thu, 16 Dec 2021 16:53:57 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36254 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234629AbhLPVx4 (ORCPT ); Thu, 16 Dec 2021 16:53:56 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4D7BFC061574 for ; Thu, 16 Dec 2021 13:53:56 -0800 (PST) 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=Yd8tiX8+x5pXfOFC4eElbWaK5eHhiwmaYRCfz7A9fM4=; b=cHMTBQ+svuDgXMImHP699DDS3K k6HtE/PXCUE/5o4x3XPmZoNajs3H4wqcV6e3UxcZhuhNXDZOZ8pWXRmRNPTJh0GX3i6p1wArCSG9d ZL3tWcUpqdu37q/3BlANIeUNCP4n81A42S/ad59ATiAFzXoDDtzGtINuiVhfdfN3SBD4KpJI2hFzm M8kcPvpp72AzUEy5kikllthnq5QduRTqTJ2v15sB+1wN2t4rIcSIhEHGpPBEt8ZIY49bJdCqRseNj P3QPsj9D436d1IId7BYHGYw/qmqehqk/wvgZVcK8oQIwfyI/PdO2xrRztagcrnd7vmPIh2E2uRsiW FrzsgsjA==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1mxyhE-00FzYC-TR; Thu, 16 Dec 2021 21:53:52 +0000 From: "Matthew Wilcox (Oracle)" To: Kees Cook Cc: "Matthew Wilcox (Oracle)" , linux-mm@kvack.org, linux-hardening@vger.kernel.org Subject: [PATCH v4 4/4] usercopy: Remove HARDENED_USERCOPY_PAGESPAN Date: Thu, 16 Dec 2021 21:53:51 +0000 Message-Id: <20211216215351.3811471-5-willy@infradead.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20211216215351.3811471-1-willy@infradead.org> References: <20211216215351.3811471-1-willy@infradead.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org There isn't enough information to make this a useful check any more; the useful parts of it were moved in earlier patches, so remove this set of checks now. Signed-off-by: Matthew Wilcox (Oracle) --- mm/usercopy.c | 61 ------------------------------------------------ security/Kconfig | 13 +---------- 2 files changed, 1 insertion(+), 73 deletions(-) diff --git a/mm/usercopy.c b/mm/usercopy.c index db2e8c4f79fd..1ee1f0d74828 100644 --- a/mm/usercopy.c +++ b/mm/usercopy.c @@ -157,64 +157,6 @@ static inline void check_bogus_address(const unsigned long ptr, unsigned long n, usercopy_abort("null address", NULL, to_user, ptr, n); } -/* Checks for allocs that are marked in some way as spanning multiple pages. */ -static inline void check_page_span(const void *ptr, unsigned long n, - struct page *page, bool to_user) -{ -#ifdef CONFIG_HARDENED_USERCOPY_PAGESPAN - const void *end = ptr + n - 1; - bool is_reserved, is_cma; - - /* - * Sometimes the kernel data regions are not marked Reserved (see - * check below). And sometimes [_sdata,_edata) does not cover - * rodata and/or bss, so check each range explicitly. - */ - - /* Allow reads of kernel rodata region (if not marked as Reserved). */ - if (ptr >= (const void *)__start_rodata && - end <= (const void *)__end_rodata) { - if (!to_user) - usercopy_abort("rodata", NULL, to_user, 0, n); - return; - } - - /* Allow kernel data region (if not marked as Reserved). */ - if (ptr >= (const void *)_sdata && end <= (const void *)_edata) - return; - - /* Allow kernel bss region (if not marked as Reserved). */ - if (ptr >= (const void *)__bss_start && - end <= (const void *)__bss_stop) - return; - - /* Is the object wholly within one base page? */ - if (likely(((unsigned long)ptr & (unsigned long)PAGE_MASK) == - ((unsigned long)end & (unsigned long)PAGE_MASK))) - return; - - /* - * Reject if range is entirely either Reserved (i.e. special or - * device memory), or CMA. Otherwise, reject since the object spans - * several independently allocated pages. - */ - is_reserved = PageReserved(page); - is_cma = is_migrate_cma_page(page); - if (!is_reserved && !is_cma) - usercopy_abort("spans multiple pages", NULL, to_user, 0, n); - - for (ptr += PAGE_SIZE; ptr <= end; ptr += PAGE_SIZE) { - page = virt_to_head_page(ptr); - if (is_reserved && !PageReserved(page)) - usercopy_abort("spans Reserved and non-Reserved pages", - NULL, to_user, 0, n); - if (is_cma && !is_migrate_cma_page(page)) - usercopy_abort("spans CMA and non-CMA pages", NULL, - to_user, 0, n); - } -#endif -} - static inline void check_heap_object(const void *ptr, unsigned long n, bool to_user) { @@ -257,9 +199,6 @@ static inline void check_heap_object(const void *ptr, unsigned long n, unsigned long offset = ptr - page_address(page); if (offset + n > page_size(page)) usercopy_abort("page alloc", NULL, to_user, offset, n); - } else { - /* Verify object does not incorrectly span multiple pages. */ - check_page_span(ptr, n, page, to_user); } } diff --git a/security/Kconfig b/security/Kconfig index 0b847f435beb..5b289b329a51 100644 --- a/security/Kconfig +++ b/security/Kconfig @@ -160,20 +160,9 @@ config HARDENED_USERCOPY copy_from_user() functions) by rejecting memory ranges that are larger than the specified heap object, span multiple separately allocated pages, are not on the process stack, - or are part of the kernel text. This kills entire classes + or are part of the kernel text. This prevents entire classes of heap overflow exploits and similar kernel memory exposures. -config HARDENED_USERCOPY_PAGESPAN - bool "Refuse to copy allocations that span multiple pages" - depends on HARDENED_USERCOPY - depends on EXPERT - help - When a multi-page allocation is done without __GFP_COMP, - hardened usercopy will reject attempts to copy it. There are, - however, several cases of this in the kernel that have not all - been removed. This config is intended to be used only while - trying to find such users. - config FORTIFY_SOURCE bool "Harden common str/mem functions against buffer overflows" depends on ARCH_HAS_FORTIFY_SOURCE