From patchwork Mon Jul 29 02:37:13 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yafang Shao X-Patchwork-Id: 13744237 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 E08E1C3DA64 for ; Mon, 29 Jul 2024 02:40:02 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 66FD310E214; Mon, 29 Jul 2024 02:40:02 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.b="ZT50cd18"; dkim-atps=neutral Received: from mail-pf1-f172.google.com (mail-pf1-f172.google.com [209.85.210.172]) by gabe.freedesktop.org (Postfix) with ESMTPS id BB15B10E214 for ; Mon, 29 Jul 2024 02:40:01 +0000 (UTC) Received: by mail-pf1-f172.google.com with SMTP id d2e1a72fcca58-70d1cbbeeaeso1794404b3a.0 for ; Sun, 28 Jul 2024 19:40:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1722220801; x=1722825601; 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=8rSpj4+mjUH2uIm/J6/DitPwV6C8fJ6cAywoYkpJrFY=; b=ZT50cd18oJh/PY9poWqQ4o7iRf9PmUwzYuibj0JWQGksOMad4sdI7J6xfQ0MB4u4qy twwPtRjW6fnrPyh39ITbwxf1BjrJ6Whql+xSjErKYzom4tEUk1wdKeHrbr3UfIo4+yZP zAwjHHklz/VA5otsFacbzaV2PgHEaIrR+FqSSO+S5ofqNLh5csd7SChP1B9Vr8VdmqHJ czgNLjuONm1i1LPLd1ukMfqLcLwKxRXos7ggd74DyPpQKfVmptmA8Yoy1jQqqeC7u6x4 nzDcsKc3Cc09VIruxPof3pvz6Lo8oA2OL2as1iZNgmEaTCwbVnMYdGpXWfgiEJB6tdcF iLTA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1722220801; x=1722825601; 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=8rSpj4+mjUH2uIm/J6/DitPwV6C8fJ6cAywoYkpJrFY=; b=kmVEWxi3ww2zSUG8Q2yO4nUBTKqrdWqZZCrlbRNtYCP/50ut3v4u/gi/diPGvYXyNz CRnlWOeQA24B4MLd7401s65zgaWoZn/kBh+MmtUW7DdKRyS7YZbTT9ucRSZxA8CvXv+u UhjLuz0iu+FqyJJpEjNnk7FYer+5SMeXUsxfFgr8o5ZnJ9tiKFctp7k/l0z+IL/eRl2B +V5+CRGsB+U+Ug5mbt6ugq3Dfnxd2tpPygE8zmX43lqY1d3mg0pckVMDEFe990bpBsqV J0xtVAsErAh2d+dEr9UJy9W2xV71JHgWjZa/fGSeu/rh7n4/dSiDikX6O30IvWpCCEId 4bXg== X-Forwarded-Encrypted: i=1; AJvYcCU6oiU0fVlLiA09qs3RU4GeYFmq+rRNf9VU0JXAVaFjk2kQvOEBFGvOZZt06+A8fa+Vs5jZl2XLRiuy4McZV7dirFmdV7bkNawODj6XipN7 X-Gm-Message-State: AOJu0YzQbUWcSYZVtCVtsPf9yv3RCSdu6+tdaUKt77T24Yf9/O3xDq/C DGiXTdlgX76XTURlsgjWx3o7+H6g5toysBrm+8Uo2Oi80G124s5x X-Google-Smtp-Source: AGHT+IGTYP+13dgbaXUTcOaiyJPHukRZsfD9pPSgLtBCe0th4rvzpLqZDHRAsUFno3V6NU5AaOlIiQ== X-Received: by 2002:a05:6a20:a105:b0:1c0:f2d9:a452 with SMTP id adf61e73a8af0-1c4a12a2e61mr4874235637.13.1722220801130; Sun, 28 Jul 2024 19:40:01 -0700 (PDT) Received: from localhost.localdomain ([223.104.210.31]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-2cf28c55a38sm7332247a91.10.2024.07.28.19.39.42 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Sun, 28 Jul 2024 19:40:00 -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 v4 05/11] mm/util: Fix possible race condition in kstrdup() Date: Mon, 29 Jul 2024 10:37:13 +0800 Message-Id: <20240729023719.1933-6-laoar.shao@gmail.com> X-Mailer: git-send-email 2.30.1 (Apple Git-130) In-Reply-To: <20240729023719.1933-1-laoar.shao@gmail.com> References: <20240729023719.1933-1-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 c9e519e6811f..41c7875572ed 100644 --- a/mm/util.c +++ b/mm/util.c @@ -60,8 +60,14 @@ 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);