From patchwork Thu Apr 14 20:17:27 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 562202 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 3E259C433EF for ; Thu, 14 Apr 2022 20:17:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346205AbiDNUT4 (ORCPT ); Thu, 14 Apr 2022 16:19:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33156 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238317AbiDNUTz (ORCPT ); Thu, 14 Apr 2022 16:19:55 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 72D38EB0A3; Thu, 14 Apr 2022 13:17:29 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 0F53261ECB; Thu, 14 Apr 2022 20:17:29 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 62FEDC385A1; Thu, 14 Apr 2022 20:17:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1649967448; bh=9wFoZvxctteNY0ku76s0j2cfjUOViAsXz3arNOYcvJU=; h=Date:To:From:Subject:From; b=jTPfs5rCj1PdUxwEIx7x+bbg3aBLhq9ixUT5qwodj8nOKiRYqAiWd0/bS2odmu0C+ x21zBHxOLMqqVnTaMYR0vPNca0K9wkOzIqjW/yzXoAFzUO+OGUqLDaCYGmSoEq5+uv soGtzJgE20iXG97lp4HqxbXwYylfXKrCVrREDt78= Date: Thu, 14 Apr 2022 13:17:27 -0700 To: mm-commits@vger.kernel.org, stable@vger.kernel.org, shuah@kernel.org, sidhartha.kumar@oracle.com, akpm@linux-foundation.org From: Andrew Morton Subject: + selftest-vm-verify-remap-destination-address-in-mremap_test.patch added to -mm tree Message-Id: <20220414201728.62FEDC385A1@smtp.kernel.org> Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch titled Subject: selftest/vm: verify remap destination address in mremap_test has been added to the -mm tree. Its filename is selftest-vm-verify-remap-destination-address-in-mremap_test.patch This patch should soon appear at https://ozlabs.org/~akpm/mmots/broken-out/selftest-vm-verify-remap-destination-address-in-mremap_test.patch and later at https://ozlabs.org/~akpm/mmotm/broken-out/selftest-vm-verify-remap-destination-address-in-mremap_test.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Sidhartha Kumar Subject: selftest/vm: verify remap destination address in mremap_test Because mremap does not have a NOREPLACE flag, it can destroy existing mappings. This can cause a segfault if regions such as text are destroyed. Verify the requested mremap destination address does not overlap any existing mappings by using mmap's FIXED_NOREPLACE flag and checking for the EEXIST error code. Keep incrementing the destination address until a valid mapping is found or max address is reached. Link: https://lkml.kernel.org/r/20220414171529.62058-3-sidhartha.kumar@oracle.com Signed-off-by: Sidhartha Kumar Cc: Shuah Khan Cc: Signed-off-by: Andrew Morton --- a/tools/testing/selftests/vm/mremap_test.c~selftest-vm-verify-remap-destination-address-in-mremap_test +++ a/tools/testing/selftests/vm/mremap_test.c @@ -10,6 +10,7 @@ #include #include #include +#include #include "../kselftest.h" @@ -64,6 +65,34 @@ enum { .expect_failure = should_fail \ } +/* + * Returns 0 if the requested remap region overlaps with an + * existing mapping (e.g text, stack) else returns 1. + */ +static int remap_region_valid(void *addr, unsigned long long size) +{ + void *remap_addr = NULL; + int ret = 1; + + if ((unsigned long long) addr > ULLONG_MAX - size) { + ksft_print_msg("Can't find a valid region to remap to\n"); + exit(KSFT_SKIP); + } + + /* Use MAP_FIXED_NOREPLACE flag to ensure region is not mapped */ + remap_addr = mmap(addr, size, PROT_READ | PROT_WRITE, + MAP_FIXED_NOREPLACE | MAP_ANONYMOUS | MAP_SHARED, + -1, 0); + if (remap_addr == MAP_FAILED) { + if (errno == EEXIST) + ret = 0; + } else { + munmap(remap_addr, size); + } + + return ret; +} + /* Returns mmap_min_addr sysctl */ static unsigned long long get_mmap_min_addr(void) { @@ -179,6 +208,13 @@ static long long remap_region(struct con if (!((unsigned long long) addr & c.dest_alignment)) addr = (void *) ((unsigned long long) addr | c.dest_alignment); + /* Don't destroy existing mappings unless expected to overlap */ + while (!remap_region_valid(addr, c.region_size)) { + if (c.overlapping) + break; + addr += c.src_alignment; + } + clock_gettime(CLOCK_MONOTONIC, &t_start); dest_addr = mremap(src_addr, c.region_size, c.region_size, MREMAP_MAYMOVE|MREMAP_FIXED, (char *) addr);