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Mon, 20 Jan 2025 01:00:54 -0800 (PST) Received: from localhost ([157.82.203.37]) by smtp.gmail.com with UTF8SMTPSA id 41be03b00d2f7-a9bdf0b50c6sm5386971a12.68.2025.01.20.01.00.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 20 Jan 2025 01:00:53 -0800 (PST) From: Akihiko Odaki Date: Mon, 20 Jan 2025 18:00:11 +0900 Subject: [PATCH net-next v4 2/9] tun: Avoid double-tracking iov_iter length changes Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20250120-tun-v4-2-ee81dda03d7f@daynix.com> References: <20250120-tun-v4-0-ee81dda03d7f@daynix.com> In-Reply-To: <20250120-tun-v4-0-ee81dda03d7f@daynix.com> To: Jonathan Corbet , Willem de Bruijn , Jason Wang , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , "Michael S. Tsirkin" , Xuan Zhuo , Shuah Khan , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-kselftest@vger.kernel.org, Yuri Benditovich , Andrew Melnychenko , Stephen Hemminger , gur.stavi@huawei.com, devel@daynix.com, Akihiko Odaki Cc: Willem de Bruijn X-Mailer: b4 0.14.2 tun_get_user() used to track the length of iov_iter with another variable. We can use iov_iter_count() to determine the current length to avoid such chores. Signed-off-by: Akihiko Odaki Reviewed-by: Willem de Bruijn --- drivers/net/tun.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/drivers/net/tun.c b/drivers/net/tun.c index 452fc5104260fe7ff5fdd5cedc5d2647cbe35c79..bd272b4736fb7e9004f7d91dc83c69af5239bfe0 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -1742,7 +1742,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile, struct tun_pi pi = { 0, cpu_to_be16(ETH_P_IP) }; struct sk_buff *skb; size_t total_len = iov_iter_count(from); - size_t len = total_len, align = tun->align, linear; + size_t len, align = tun->align, linear; struct virtio_net_hdr gso = { 0 }; int good_linear; int copylen; @@ -1754,9 +1754,8 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile, enum skb_drop_reason drop_reason = SKB_DROP_REASON_NOT_SPECIFIED; if (!(tun->flags & IFF_NO_PI)) { - if (len < sizeof(pi)) + if (iov_iter_count(from) < sizeof(pi)) return -EINVAL; - len -= sizeof(pi); if (!copy_from_iter_full(&pi, sizeof(pi), from)) return -EFAULT; @@ -1765,9 +1764,8 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile, if (tun->flags & IFF_VNET_HDR) { int vnet_hdr_sz = READ_ONCE(tun->vnet_hdr_sz); - if (len < vnet_hdr_sz) + if (iov_iter_count(from) < vnet_hdr_sz) return -EINVAL; - len -= vnet_hdr_sz; if (!copy_from_iter_full(&gso, sizeof(gso), from)) return -EFAULT; @@ -1776,11 +1774,13 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile, tun16_to_cpu(tun, gso.csum_start) + tun16_to_cpu(tun, gso.csum_offset) + 2 > tun16_to_cpu(tun, gso.hdr_len)) gso.hdr_len = cpu_to_tun16(tun, tun16_to_cpu(tun, gso.csum_start) + tun16_to_cpu(tun, gso.csum_offset) + 2); - if (tun16_to_cpu(tun, gso.hdr_len) > len) + if (tun16_to_cpu(tun, gso.hdr_len) > iov_iter_count(from)) return -EINVAL; iov_iter_advance(from, vnet_hdr_sz - sizeof(gso)); } + len = iov_iter_count(from); + if ((tun->flags & TUN_TYPE_MASK) == IFF_TAP) { align += NET_IP_ALIGN; if (unlikely(len < ETH_HLEN ||