From mboxrd@z Thu Jan 1 00:00:00 1970 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 D3895C433F5 for ; Wed, 27 Apr 2022 22:46:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237072AbiD0Wtp (ORCPT ); Wed, 27 Apr 2022 18:49:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49328 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236994AbiD0Wtj (ORCPT ); Wed, 27 Apr 2022 18:49:39 -0400 Received: from mail-ed1-x52e.google.com (mail-ed1-x52e.google.com [IPv6:2a00:1450:4864:20::52e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 11BE23FBDB for ; Wed, 27 Apr 2022 15:46:21 -0700 (PDT) Received: by mail-ed1-x52e.google.com with SMTP id g20so3548999edw.6 for ; Wed, 27 Apr 2022 15:46:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=Ue6rVu6i+LhfCao8kUR1Z6Jfs0LQjlJynwWVcrWd6VM=; b=Gndc1RCGkDncdLnhWZGKEMfSDA6RiY6gYsq2cfbAeZNK4nrXaz/6N1hr6sqvdr311j JWoa0bmCoQ403+CD/hq+Sfq2bCXRvGzfLvjnwjye9dkw8VgX78EKPb1PHzbS6qOQ4x67 IfrxMTZCU0wjTwJB4VIaKx7ERPHXDEo7k7W8VQosJNY/stX38nDCk3GR6BRnaPrk7dmm 6fFhd/zSnRznh4bRhxzaNHYIxwfYNBvel6PUZnkpkDdpVak3IFPGVWSZ5NWYIn9gwwkR ZxNPOZKzDXvQu/0bdtnoy4oXB1JsUhap5CcqYbV3WUp3mfjo3KFJ+zFdt4MxQlGAZ+4Q G55w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=Ue6rVu6i+LhfCao8kUR1Z6Jfs0LQjlJynwWVcrWd6VM=; b=UMd2BBO5xHUx6ZBgYmfeMdKaxi+L+oYTjAgnc6Gd7EPEhzzx223h8oi8TVNu58LMZX XM/hlGft+e3iqBjDr5hDJZcJvrpD1AzwQ1TdU1otyC3VA5iPPx+XP1nmDXmM+tMF3Aw+ UQlYBodtUDgNgcaTtBJcFRxHyCb0UTX03Q2wxG2kwmUid/zyr/DkrVCVzMMiuoh79+Zn J6MPcvL68xc+Hb1Mdo2pOtL4HmDIJuflTHDLSU5Q35sE6kS4OYaL9QsWNbHKegcTFE/S lZrmx/07WMGB/L5OOZv2qWW7oVJbB6MVJ7XV5DW+FJD96RBmBvcv9D7iC4VuTP1OHQKo dEVw== X-Gm-Message-State: AOAM530bLckXxo9f10QbGd0FdBOuhfc2Hz5XPbpU776KVedpOFouSFp1 v+gN89lI2KV+e/mlAnZVw5TX0Jms1Y4= X-Google-Smtp-Source: ABdhPJxd0YZSftPkxD/+f96yvJ2QI3MqleeuNByzeM6djihWCYdTQgVG4j7ZbQTiHW3uDizGz0UT8Q== X-Received: by 2002:aa7:ce84:0:b0:425:d2e0:a75f with SMTP id y4-20020aa7ce84000000b00425d2e0a75fmr25946415edv.263.1651099579646; Wed, 27 Apr 2022 15:46:19 -0700 (PDT) Received: from nlaptop.localdomain (ptr-dtfv0poj8u7zblqwbt6.18120a2.ip6.access.telenet.be. [2a02:1811:cc83:eef0:f2b6:6987:9238:41ca]) by smtp.gmail.com with ESMTPSA id o14-20020a170906774e00b006d5b915f27dsm7351657ejn.169.2022.04.27.15.46.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 27 Apr 2022 15:46:19 -0700 (PDT) From: Niels Dossche To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Mina Almasry , Niels Dossche Subject: [PATCH 0/2] mm: mremap: fix sign for EFAULT error return value Date: Thu, 28 Apr 2022 00:44:37 +0200 Message-Id: <20220427224439.23828-1-dossche.niels@gmail.com> X-Mailer: git-send-email 2.35.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The mremap syscall is supposed to return a pointer to the new virtual memory area on success, and a negative value of the error code in case of failure. Currently, EFAULT is returned when the VMA is not found, instead of -EFAULT. The users of this syscall will therefore believe the syscall succeeded in case the VMA didn't exist, as it returns a pointer to address 0xe (0xe being the value of EFAULT). This can easily be reproduced by the following C program. I expected mremap to fail, but it does not. If the bug is present, it will print 0xe, otherwise the mremap will fail. The patchset contains two patches: one that fixes the error, and one that adds a small test case. #define _GNU_SOURCE #include #include int main() { // Get pointer that's definitely not mapped void* ptr = mmap(NULL, 4096, PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); if (ptr == MAP_FAILED) { perror("mmap"); return 1; } int err = munmap(ptr, 4096); if (err < 0) { perror("munmap"); return 1; } // Remap unexisting VMA ptr = mremap(ptr, 4096, 4096, 0); if (ptr == MAP_FAILED) { perror("mremap"); return 1; } printf("%p\n", ptr); return 0; } Niels Dossche (2): mm: mremap: fix sign for EFAULT error return value selftest/vm: test that mremap fails on non-existent vma mm/mremap.c | 2 +- tools/testing/selftests/vm/hugepage-mremap.c | 6 ++++++ 2 files changed, 7 insertions(+), 1 deletion(-) -- 2.35.2