From patchwork Wed Aug 28 03:03:18 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yafang Shao X-Patchwork-Id: 13780414 X-Patchwork-Delegate: paul@paul-moore.com Received: from mail-pg1-f169.google.com (mail-pg1-f169.google.com [209.85.215.169]) (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 B7EDE132132; Wed, 28 Aug 2024 03:04:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.169 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724814256; cv=none; b=mzd857QP9MwAXspnmulp80RtFfvWyRnh2GgYqKdxwrJfjI8KT4stDlkd7vPUxRtRaZ6xciqmFNPJ/d+SslhxHCumcZZZiKcAxyttfDt+9Xo/7bet2sZYxN6j3Aja4mChA+DrdQ3P/AHSYHOy/WOesoOzOmNFaRjYInpNYDclxf0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724814256; c=relaxed/simple; bh=AKUKeXG3rR4W64tTAZjDR7220EmBnpL03mh0NUmcuXM=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=fQn53caO6gzFsLGUSuPKbT/DvPxpD5g6yc3V/ard1A14A5SxQ1U6KSvk+HblGmpFJkmlsM/o0MPRBe5Hr/scdYow4KkBM9ifoOsNclRxJTItBJ3m2DQfBVdTeeCb5vBY+L8lZB9pIg/xzm37tC0dBd7CeGq0OIXjOl+yjWyH3u4= 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=AE1XsnkA; arc=none smtp.client-ip=209.85.215.169 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="AE1XsnkA" Received: by mail-pg1-f169.google.com with SMTP id 41be03b00d2f7-7c1324be8easo120148a12.1; Tue, 27 Aug 2024 20:04:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1724814254; x=1725419054; 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=N9R7Mhbk+Se4PIDhpm0/p6nrldMPUtb+oC6vNd91DMo=; b=AE1XsnkAw14RfqXi6Nl1oqdu7S2gdUsvqRT7RHeuW5mZ/z9TLNKk1F+Oxe3/d8t++0 tBpNCs/w43yuEoFopclB1plI6IZsFBXXa7cZUdBNug/MVqcUsl3GQ61Dxt3hT8Ottk9d pJkyXkAHA023bAwEUCiX+SrhyGH0grPpFlt2a6OQMOPH8+vBSbLWzCt5IxIf6vsjsJcz bHZwjZD5Ml5p1bxnujfeCqutxK2HaADzu751Numeq8hpDoteJMVUdQ7sn7K8mrlojx+I bbbxAsDG2VeVoOLVZH93lwcx0vNVLkc0WqTCx8k26rb6Di4ZTu9aOC0e3fC5ey5Vl4Dm Z/sw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1724814254; x=1725419054; 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=N9R7Mhbk+Se4PIDhpm0/p6nrldMPUtb+oC6vNd91DMo=; b=KlfSL4Pl2h6Drwr/i1ttwkod5WSVS69cvGHTOX8jU/mEIcY6kVNhvDNVhAd55WIhrm pNXECPaQB8RYuoK2x0WuDIvl6GcTuAH2IShW7l0P3Z5zUvwTRGaTd2JeQno0Zaheu2pO I/LcqSZoayvFE56K1ZuuwJmHQw/4bsC9XbbnkkCLP4ytdMzBLfHFlxiy8cVgheb9iTbx DHjR7RhhuO1/6gDnvwv4OGISIqOsxrQSWamLlR0Nz042E2SUCN8GXOi5VCH6y3/aRtZI 6DEg1WdqCYkkRhHAl5viKAPzdzHW6DvuIrj8LM0CSv5XWNBI11KpTgJmDNjDoimsJwo+ uTGw== X-Forwarded-Encrypted: i=1; AJvYcCUF+eQr1oxnEkDm58EL8SlSWRSm8fYTtroroNrEqHaBImQiIUbnduriHCpxv5ovGNraADaBWJj3B5fBzTQieA==@vger.kernel.org, AJvYcCUF9Qd3tXnIiatWQYh6lhuA9SLcR8t957sKOkfGA8f7amLZf/IYj5B7QCP1uis1de/RN3KQMTU/0nCYw81p5//439+Uspj2@vger.kernel.org, AJvYcCW8KQY97vn9+V/psunq6WqjJnjgzyP8IJgYcddnbwOvlXm6OKGAEH9jUREdRi5S7S1DEn2Zk88yFMVJsjPJNJzoAvRJ@vger.kernel.org, AJvYcCWGBiEYMB+aQITZlPM9E7iBUWlr1J8tTg+IBfIvfZG8DWCiYMu94IR1/xXxjhz4ISfPsaFh0zZm@vger.kernel.org, AJvYcCWWtsKiNDOH6HFzEssEfnReudmg74mAj9D7KotwjYjJ4uYMwxWap/jca1rwfWOUFDe81yd/gesPlg==@vger.kernel.org, AJvYcCX59CRocOyi+vdEzgWXqEIOrBIeABgsyXF6fS+w8hS8hWhWwDDZ64Oq9H21X/qL1JFsDgAh@vger.kernel.org, AJvYcCXVRFq5BrICch8XvrWmvGV+4k6FpNIWqTXY5LMEaYs08XAqC3VAvi43XjceHYxR/W3OGDqYcQ==@vger.kernel.org X-Gm-Message-State: AOJu0YzXokGO/NSOaEljZXUG0tDMrygQUvRUnKvdnkC+1fCHStDlCXdP r86S8zi2KPSStxIxqJ6ffW+USX4An8BCSPLybL26UwCeeyyRgjYB X-Google-Smtp-Source: AGHT+IGCtw+zPOY+Vs3gCNaMxterxPo1VEjCCML55T5/9brSfwlu9kiROVQ6nSIbi2XhsLWhhe27AA== X-Received: by 2002:a17:90b:3b49:b0:2d3:d79f:e8b7 with SMTP id 98e67ed59e1d1-2d843c16e68mr1209703a91.5.1724814253885; Tue, 27 Aug 2024 20:04:13 -0700 (PDT) Received: from localhost.localdomain ([39.144.104.43]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-2d8445db8f6sm317977a91.1.2024.08.27.20.04.06 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Tue, 27 Aug 2024 20:04:13 -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 v8 5/8] mm/util: Fix possible race condition in kstrdup() Date: Wed, 28 Aug 2024 11:03:18 +0800 Message-Id: <20240828030321.20688-6-laoar.shao@gmail.com> X-Mailer: git-send-email 2.30.1 (Apple Git-130) In-Reply-To: <20240828030321.20688-1-laoar.shao@gmail.com> References: <20240828030321.20688-1-laoar.shao@gmail.com> Precedence: bulk X-Mailing-List: selinux@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 Cc: Alejandro Colomar --- mm/util.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/mm/util.c b/mm/util.c index bd283e2132e0..9a77a347c385 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 NUL termimator. + */ + buf[len - 1] = '\0'; + } return buf; } EXPORT_SYMBOL(kstrdup);