From patchwork Sat Aug 17 02:56:21 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yafang Shao X-Patchwork-Id: 13766954 Received: from mail-pl1-f177.google.com (mail-pl1-f177.google.com [209.85.214.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 20C2222334; Sat, 17 Aug 2024 02:57:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.177 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723863454; cv=none; b=f2JXWsX68P7v1F47ibo5NH2PYfIYhIrH/hF0OpGeJZz9iokcZBY0/CgtFVWNvSFW5/nMGGf636QxSn11qVw0ZxvmjJjnSsOqwg7eAj3g4KfV5bInEiIbTDOHRlO6V3OlYvjdcnYoGWXixMWri4+BmGR2CC1qkH/pP+B9d7zono0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723863454; c=relaxed/simple; bh=ads9a+vJAdf3fW1daUgzeFpk3FAtZrgaeqt3aAf0isQ=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=gXTYymEfaZJo60vcDrfSTR8jgwXADIacEdqIKsLKD6UPZJL8uc1dimeH1AItf+qhVzDgkevTIEQvkbnBto59/KgpXtJybjY4vTkI5s1vCag1tuHusEFxZF+wYobD8sS/tqjnFkElnwq4Tgw2nmkpwb8hIgoIpEqosSMfYvKgFOE= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=No9uGHvi; arc=none smtp.client-ip=209.85.214.177 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="No9uGHvi" Received: by mail-pl1-f177.google.com with SMTP id d9443c01a7336-2021537a8e6so8183015ad.2; Fri, 16 Aug 2024 19:57:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1723863452; x=1724468252; darn=vger.kernel.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=No9uGHvixrC5zhJ6Qf5/Rujx/kNuE/tx4qUC2sbmesSYXTBeOu1HLmGVuwYXv6xvD4 OFbyAz7bwd5HeyT10mLzSSEROQ4VJOqLj7o/UDzNORmVGasNcy1AlwkJZuW2uO1haagr harQUf2iU+m4WYBdER4eFDkwASWaGaDa+gxs4Rd/MZFX7GPgj/j4SaZJnUcVwnHRCZSv XuFb7OtvagPmlQ4d2/Xrsj4J2lMqH6/s47HLhOQhR6gQCieNDKYgEPFX0ZEf1KhkIwKC yGrdyIiH+VXNFX7/BA4dllwjkPHggG6XRri7Vwf4QHI9gilqa77i0/BYKiG7MjGq+Fyz OnTQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1723863452; x=1724468252; 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=N5+Zq6SO5agAtVPqpf+dS8MFArl89CsxgGy8MXfJU0AE+yUz9vUOpyB92cf3HgrGHC jxh2XEVHPrPHyiv2pFCeNeRmwXvTGi25yPgets6/bbfUj8Y03u4y4dCQT2NUQLjKlWh6 s9Ho1LuS4a/MXHfcFcWtDE7vn0uj2gW0K2FBFQnuJw03StsBLvnGyrpR17e5oljRn/iZ CrT2P3BuRGlOagRAkTkoSfXh6bq8VJeuRhBBbz3vS71LSfbCS0losAW26K/iN8wifofw QegakhNwAB1+Qq+MYhsUcdXXDaY3CrYHgXfcpNmxenWNG+AXpTOdFMM99y8c5Ikl1rC5 0phg== X-Forwarded-Encrypted: i=1; AJvYcCUB5HjKjeJc2b4AEpAWRh2VoReKiwYK0jwypBOdW7ZcJcsodpDAlNGl0IKfST3xbJ3VeWxzJzXT@vger.kernel.org, AJvYcCUgwM47wEdJUaI/gvSYXa+yPC9maR2FZPKh4x4E8SGzX0qTz5nFvDRhzRORUUjuZRrdeHXXJA==@vger.kernel.org, AJvYcCValauww7PVH4JDRq4jZnnh/AwP2h/HsFCyk/ayTXO9uBVdUtjprhVfZ4oMcSHjkev7SbVsB2SxhL5nUuxhlJvU2AYsqCns@vger.kernel.org, AJvYcCVyspMNlPOoadfMhtccXlhqHnUNcH38XUUk4svBbgSSEjeNtqFNq6tVVLqZhJM4jfB30VXYgGrCxQ==@vger.kernel.org, AJvYcCWlmvE379tCHsFz3ZFTswtREL7BmxcWcvD8E8q03S7x6Y6UMSLXqAa60tjF40R+d8Qh9grB@vger.kernel.org, AJvYcCWrO5MMs7pVb1yu9N+aC6EorCnLYTr+Zf8zlUzisZLjeZa5SeZdSGDDOWjqgvUv2cIYw2JmMLYvTH0Kdl1xnVl23s96@vger.kernel.org, AJvYcCX61GWrt/cgfQd8YZiHu6alAARWleabAt/xc4OhxOuH5+K3gboyBcrnmC+ZlwU7zwCsS50pa4iq8wLOfeYOwg==@vger.kernel.org X-Gm-Message-State: AOJu0YyDn2/3H9yvjYEafBUGDxet94X4TJPzYw2d1+gFpDZbRwcq7QVI FlWYl3X6Wr5e9IV+Qcn2bANMucxKYOakq22obqT1sya08jKENEls X-Google-Smtp-Source: AGHT+IF3ZN+4FrJiR5tCQknEVTwkbUbAx80SeY+AiIkjp+qgoruwIjB5dCv+k+zHBrTId5++7+R3wA== X-Received: by 2002:a17:902:cccc:b0:1fb:7b01:7980 with SMTP id d9443c01a7336-20203af4193mr61360745ad.0.1723863452450; Fri, 16 Aug 2024 19:57:32 -0700 (PDT) Received: from localhost.localdomain ([183.193.177.10]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-201f031c5e1sm31801785ad.94.2024.08.16.19.57.24 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 16 Aug 2024 19:57:31 -0700 (PDT) From: Yafang Shao To: akpm@linux-foundation.org Cc: torvalds@linux-foundation.org, alx@kernel.org, justinstitt@google.com, 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 v7 5/8] mm/util: Fix possible race condition in kstrdup() Date: Sat, 17 Aug 2024 10:56:21 +0800 Message-Id: <20240817025624.13157-6-laoar.shao@gmail.com> X-Mailer: git-send-email 2.30.1 (Apple Git-130) In-Reply-To: <20240817025624.13157-1-laoar.shao@gmail.com> References: <20240817025624.13157-1-laoar.shao@gmail.com> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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);