From patchwork Mon Aug 12 02:29:29 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yafang Shao X-Patchwork-Id: 13760022 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 gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C6B2DC52D7C for ; Mon, 12 Aug 2024 02:31:07 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 5458C10E045; Mon, 12 Aug 2024 02:31:07 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.b="GVcrQ7Ke"; dkim-atps=neutral Received: from mail-pl1-f181.google.com (mail-pl1-f181.google.com [209.85.214.181]) by gabe.freedesktop.org (Postfix) with ESMTPS id 7D3C310E045 for ; Mon, 12 Aug 2024 02:31:06 +0000 (UTC) Received: by mail-pl1-f181.google.com with SMTP id d9443c01a7336-1fc4fccdd78so25765335ad.2 for ; Sun, 11 Aug 2024 19:31:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1723429866; x=1724034666; darn=lists.freedesktop.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=Dg8K6fIsZQLFiS7Xpg/1YZlm81yjN4oHJWyrWmInMGw=; b=GVcrQ7Ke8FKjAzjNy2ts4M20MWHF7VHqtir/iVsrxwiiNS9Ikw5ttI6i4s4Lw4dWSQ nLA+FM+6239tzMnBzkhAfrZwjuGqrWyY8sq6fIRx+EaJAfZM58UbPL9ZUvW4NLJ4nkc9 tVt6haLTWauf9B5pp8fmsHR3WHUbCMyLGluCjlv9yuMOswMC8SfWRPNvSs4LK5ON7Ddz rb5LmSLl08R8Gzr2IsFskwObk98TKCtxCmxwcEJ1PbbAhITrjyKH653sj5SohUIy+P3S HeiSN9Qt7E/9Ky7mle1y3FBPCaoqmX4xVIPcnvt1zcAHI34N2mSCOTalg4fsuiygVvUB XGUA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1723429866; x=1724034666; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=Dg8K6fIsZQLFiS7Xpg/1YZlm81yjN4oHJWyrWmInMGw=; b=KzuLasdK37kUs8+sfx37Hu1syT06dvujNX37kT1nByewEykzWJz8mqxUThMykWQSBG qdRfBoZ8HvPLcJxFw0gOsdkPC7RLRZumJrxWMmK5Eu1CCNhvQZAj7rIeq0wRd1/bZshd XRuIz1JSr1qbeGvrZo1Av6j7d7O0YiJBjhMMO8+dRWY0gfQJ5y7+QV6NmD1FaM3p6C8X L4NK+B7e+z3h7tUr0YYEkZd02xSZUX7CqgeRwzeXMl8oydcZW/eeElGfQw1xDed6lV4k sivt59aUlcPGKAbTV/be0ziOVFixGbe86BEbTEjbQYRtmK0PzYlF1L7YPLS9d3Q5TP0J yCeQ== X-Forwarded-Encrypted: i=1; AJvYcCUIavtq5asB5o9TLMM+/34nU+5jVU6isU+zXBU4pCdMF3fULaMPTRLki5Nh+3Gw104xfzR7g2lPtAePsfMZ6UrM5OE0IMZrngUxkmYriPrs X-Gm-Message-State: AOJu0Yx5GJs+ndHuerLham7esluaM62nC8Ak6gVeJNGjejqje9By+b63 zOztGkJjMSM5lQmzn/1HdlSUuauWPwXritu3OB6vmRyBbCXKz9Wx X-Google-Smtp-Source: AGHT+IGpTCkxya5k7tDP0eeWIg02IZrGkBb+Xs7WqcLI3e7hWnKKPF02puCEAAGLT4aj9e0Erpx/iw== X-Received: by 2002:a17:902:cccf:b0:1f7:1655:825c with SMTP id d9443c01a7336-200ae5a8934mr50792845ad.36.1723429865812; Sun, 11 Aug 2024 19:31:05 -0700 (PDT) Received: from localhost.localdomain ([39.144.39.162]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-200bb9fed69sm27884765ad.188.2024.08.11.19.30.59 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Sun, 11 Aug 2024 19:31:05 -0700 (PDT) From: Yafang Shao To: akpm@linux-foundation.org Cc: torvalds@linux-foundation.org, ebiederm@xmission.com, alexei.starovoitov@gmail.com, rostedt@goodmis.org, catalin.marinas@arm.com, penguin-kernel@i-love.sakura.ne.jp, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, audit@vger.kernel.org, linux-security-module@vger.kernel.org, selinux@vger.kernel.org, bpf@vger.kernel.org, netdev@vger.kernel.org, dri-devel@lists.freedesktop.org, Yafang Shao Subject: [PATCH v6 5/9] mm/util: Fix possible race condition in kstrdup() Date: Mon, 12 Aug 2024 10:29:29 +0800 Message-Id: <20240812022933.69850-6-laoar.shao@gmail.com> X-Mailer: git-send-email 2.30.1 (Apple Git-130) In-Reply-To: <20240812022933.69850-1-laoar.shao@gmail.com> References: <20240812022933.69850-1-laoar.shao@gmail.com> MIME-Version: 1.0 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" In kstrdup(), it is critical to ensure that the dest string is always NUL-terminated. However, potential race condidtion can occur between a writer and a reader. Consider the following scenario involving task->comm: reader writer len = strlen(s) + 1; strlcpy(tsk->comm, buf, sizeof(tsk->comm)); memcpy(buf, s, len); In this case, there is a race condition between the reader and the writer. The reader calculate the length of the string `s` based on the old value of task->comm. However, during the memcpy(), the string `s` might be updated by the writer to a new value of task->comm. If the new task->comm is larger than the old one, the `buf` might not be NUL-terminated. This can lead to undefined behavior and potential security vulnerabilities. Let's fix it by explicitly adding a NUL-terminator. Signed-off-by: Yafang Shao Cc: Andrew Morton --- mm/util.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/mm/util.c b/mm/util.c index 983baf2bd675..4542d8a800d9 100644 --- a/mm/util.c +++ b/mm/util.c @@ -62,8 +62,14 @@ char *kstrdup(const char *s, gfp_t gfp) len = strlen(s) + 1; buf = kmalloc_track_caller(len, gfp); - if (buf) + if (buf) { memcpy(buf, s, len); + /* During memcpy(), the string might be updated to a new value, + * which could be longer than the string when strlen() is + * called. Therefore, we need to add a null termimator. + */ + buf[len - 1] = '\0'; + } return buf; } EXPORT_SYMBOL(kstrdup);