From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: ARC-Seal: i=1; a=rsa-sha256; t=1525988989; cv=none; d=google.com; s=arc-20160816; b=I35UhPg/zsLlHh9D2QCPDNaU7BJLwu+wyxjMrCK34ZBx5uopodJN9c5SQVuvUlTyad pXSjEte3sP4JH/kJJ2aouDG0YglPTqanLlIOSXjdd9F836h58K0+JDPqGflScKVU9SHD PjHZEa/U0OfdmHbkGVCDCapP/9BvP3brTIvzXqPwkvBh2G2HwSlW84dWJLyhthFoL1ko yaoFY2I47F0dMV9TLkMSSo74maAmXxm5J0LDuGI8Dtn1aT0PlTLfy7tSTHGGZNsnrAtt Lk3DbynxZczSbAoTgKUbz8B41nmQOo711/CQeybMMzgrTLD1DM+KFI5NJGbHJ6SYcMB7 cYWw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=cc:to:subject:message-id:date:from:references:in-reply-to :mime-version:dkim-signature:arc-authentication-results; bh=DSFWYJzFM6jJ60Yq/XuiwoRm/dSecebxbD5Jpc9pygw=; b=grfCcGNO1KQTYupOrH7yx7GpUWC4dYJiroN4d8mStoIO5XeNFF5gM6D676iPWqRbKR M74tv9Sj90ugJrLWE8s71P8EBTZQNkWbGNx4yxLpK7Xj7Mf45f9SpXKnL3bDOU3Hp7B0 EknhODv6NVukNY6gJQTU7pJMppHUvK91ZPxJGWkhT15Go4OsIA3WfTAsVm5iALn+sPRX 0R2zei/e/QJbM6NzHa19HM8le8H/WYRATAxAdhPNsof7kjhifsApopVNP3hyf7QEdQ8t Hq9JI//k3lXNYxf14iPJvvotjlHVN5m6yuzf1WF27jH9YcMAZ5BYXhF3GOAdEELASfFO XR6g== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=JcO4wZ3O; spf=pass (google.com: domain of willemdebruijn.kernel@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=willemdebruijn.kernel@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=JcO4wZ3O; spf=pass (google.com: domain of willemdebruijn.kernel@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=willemdebruijn.kernel@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com X-Google-Smtp-Source: AB8JxZoT3s7JlQPfCCkVmX+Z9FhMHMaVpnAQm72/jTKhE9LuVeGjjkB4eyuvdWBmTYbdENZTdbOHCIClJry7sO7dJHU= MIME-Version: 1.0 In-Reply-To: References: <94eb2c0ce3aa27cfa40561ec2dc3@google.com> <1515048794.131759.4.camel@gmail.com> <20180509073754.GG711@sol.localdomain> From: Willem de Bruijn Date: Thu, 10 May 2018 17:49:08 -0400 Message-ID: Subject: Re: KASAN: use-after-free Read in __dev_queue_xmit To: Eric Dumazet Cc: Eric Biggers , syzbot , alexander.deucher@amd.com, Andrey Konovalov , Anoob Soman , Chris Wilson , David Miller , "Reshetova, Elena" , Greg Kroah-Hartman , Kees Cook , LKML , Mike Maloney , mchehab@kernel.org, netdev , "Rosen, Rami" , Sowmini Varadhan , syzkaller-bugs@googlegroups.com, Willem de Bruijn Content-Type: text/plain; charset="UTF-8" X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1588636556567233283?= X-GMAIL-MSGID: =?utf-8?q?1600115430776330898?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Wed, May 9, 2018 at 5:05 PM, Willem de Bruijn wrote: > On Wed, May 9, 2018 at 3:36 PM, Eric Dumazet wrote: >> >> >> On 05/09/2018 12:21 PM, Willem de Bruijn wrote: >> >>> Indeed. The skb shared info struct is zeroed by dev_validate_header >>> as a result of dev->hard_header_len exceeding skb->end - skb->data. >>> >>> Not exactly sure yet how this can happen. The hard header length space >>> is accounted for during allocation as reserved memory. But, >>> packet_alloc_skb does call skb_reserve(), moving skb->data >>> effectively beyond this reserved region. >>> >>> It may be incorrect to pass skb->data to dev_validate_header, as that >>> does not point to the start of the ll_header anymore. Still figuring out what >>> the right fix is.. The following resolves the issue. packet_alloc_skb already calls skb_reserve(skb, reserve), so now the network header should start at 0, not at reserve. If SOCK_DGRAM, dev_hard_header() calls skb_push for the link layer and returns this offset. If SOCK_RAW, we should do the same and use the reserved space to write the link layer. Now behavior is the same as in tpacket_snd. @@ -2898,19 +2911,26 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len) tlen = dev->needed_tailroom; linear = __virtio16_to_cpu(vio_le(), vnet_hdr.hdr_len); linear = max(linear, min_t(int, len, dev->hard_header_len)); skb = packet_alloc_skb(sk, hlen + tlen, hlen, len, linear, msg->msg_flags & MSG_DONTWAIT, &err); if (skb == NULL) goto out_unlock; - skb_set_network_header(skb, reserve); + skb_reset_network_header(skb); err = -EINVAL; if (sock->type == SOCK_DGRAM) { offset = dev_hard_header(skb, dev, ntohs(proto), addr, NULL, len); if (unlikely(offset < 0)) goto out_free; + } else { + skb_push(skb, dev->hard_header_len); } /* Returns -EFAULT on error */ err = skb_copy_datagram_from_iter(skb, offset, &msg->msg_iter, len);