From patchwork Tue Sep 24 15:02:56 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Dumazet X-Patchwork-Id: 13811010 X-Patchwork-Delegate: kuba@kernel.org Received: from mail-yb1-f202.google.com (mail-yb1-f202.google.com [209.85.219.202]) (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 BC5311A7ACD for ; Tue, 24 Sep 2024 15:03:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727190184; cv=none; b=kiNns4O60OaHsZY+XQfv0ROGKPUDLx4wKOsHmKakqh0McVcTiqKle9NbjdiaW5UJ0rpc+wT4bWFtvQv8LqyKzpHu8shDWIfZpWupeDIrSQb90mLTgy1cDwAQEyBvqQsZpTT/mDgKgQ8GHdjRoGH8QZbPAvBNb66RtQKXoQWCiqw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727190184; c=relaxed/simple; bh=g/dIgEpOXxK/aGWhF9her578NUVE1gj+NoH/R8tuJ3Q=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=gH39Cc2vE1/3n+6Vju5SHNrQT3slBc2i3JDUan6/Ay8oeJB89JMV1F8MWaZrNRDwXo6POIqdZfSVn4pTupQ5KOwBrIZas9k0K5LC04bwE+x7q/ckgrl9j/n+e5qZK+8mnrhLr9gJMGRYYx5gqlvKc6ba7+i1mskf2yXUxnDwC+Q= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--edumazet.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=3+e+dPJV; arc=none smtp.client-ip=209.85.219.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--edumazet.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="3+e+dPJV" Received: by mail-yb1-f202.google.com with SMTP id 3f1490d57ef6-e1a8de19f5fso7962941276.3 for ; Tue, 24 Sep 2024 08:03:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1727190182; x=1727794982; darn=vger.kernel.org; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:from:to:cc:subject:date:message-id :reply-to; bh=1dBDMWv+DBMjfMybSWWoZIriIcEpXSU8MTuNI/aEyso=; b=3+e+dPJVRighVUeGh/tyX0Cq7kJPWbTzlUo4bklnBlFs2t2XmVOux8BlTxmj4nHd7C 8vtXm5p4ypEyU7ZyQi3qjR++Q2ZeMMOuzn0j8fGitQuxCC0ggVv7FrGm9G9PM3DtGCFM Y3qnDCkaCK+IQ37pFRkcG1nxs+e3hfHvTPaIu8ecHbEl/tgy4CezIgyHr2Zom+iLpDN4 PBKO5Q4SYcoDOf/i96PdDWvg9EZBjW7NxhZFz4Y5eM5eMZAOMGrt2Q2I2J/1H1tqb6oZ 5cAz07Z/BYPs7nL8J/wcVHRZLX9ewRmWd11jUo0vw6PQXBlRg6ZB3ua3jMEk/QLLNU/J 1o8w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1727190182; x=1727794982; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=1dBDMWv+DBMjfMybSWWoZIriIcEpXSU8MTuNI/aEyso=; b=Oou1eSwZTP7QtY57o83fjv4OO4hYTz5De7x/VTSOSg3E5Fp7CXm6b5TPgdJ5tXMPSl 6QGurj8TxAStas2dXsAyfPJB1PMua7qhpoLHsQ7mmUt2OvYr4TwmWVZ0N5Dv4DsCydPq SKq7kjizZdGkj2reWCM8IL9K4JtWQP2p92p5WJ8tHyzRwBVrlNvmsC8xzbR+Zd9gXC7s CCexRBtXw3tDBxk5Klko9A4+YMd+rv9TpgC1iPZpsYVZMBaR8M0OhjzBUScCCWFGaMB8 zjOlSyeN2P0I2tGQkeVsVdcwWnoF5HQR1fnJKex+WUaGNHxy/2DAIW6in+OW+mxSLU7g W63g== X-Forwarded-Encrypted: i=1; AJvYcCWJ6oMoqvqHJWt9Dv5DyCvWpw2VHazk5GKGYSya05NMaTTaBqexu4whNJEO/XisusTX2C96y84=@vger.kernel.org X-Gm-Message-State: AOJu0YxHp3qEHiJDriJ/TjSMPZFuDQAjJ2HAQFC55z69o0KCUFpega9S kTJ6vxC7TTG7Kyby3wLDPEIp92EYFL4qhGKzYw1sVeyREd83ldHgwphGFFLub49sFCvkQy6O3jA 4ex4hzKI5CQ== X-Google-Smtp-Source: AGHT+IFni0NvOOBMnOql8JvDEsVS6N5W4+LZv/RPNAv+Q0p/UCI5VP/nithd2GngWw0rH9uBxthK3tfx9GYeHw== X-Received: from edumazet1.c.googlers.com ([fda3:e722:ac3:cc00:f7:ea0b:ac12:11d6]) (user=edumazet job=sendgmr) by 2002:a25:df43:0:b0:e1a:23f2:a0e4 with SMTP id 3f1490d57ef6-e2250cd3bf4mr37800276.10.1727190181330; Tue, 24 Sep 2024 08:03:01 -0700 (PDT) Date: Tue, 24 Sep 2024 15:02:56 +0000 In-Reply-To: <20240924150257.1059524-1-edumazet@google.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240924150257.1059524-1-edumazet@google.com> X-Mailer: git-send-email 2.46.0.792.g87dc391469-goog Message-ID: <20240924150257.1059524-2-edumazet@google.com> Subject: [PATCH net 1/2] net: avoid potential underflow in qdisc_pkt_len_init() with UFO From: Eric Dumazet To: "David S . Miller" , Jakub Kicinski , Paolo Abeni Cc: David Ahern , netdev@vger.kernel.org, Willem de Bruijn , Jonathan Davies , eric.dumazet@gmail.com, Eric Dumazet , syzbot X-Patchwork-Delegate: kuba@kernel.org After commit 7c6d2ecbda83 ("net: be more gentle about silly gso requests coming from user") virtio_net_hdr_to_skb() had sanity check to detect malicious attempts from user space to cook a bad GSO packet. Then commit cf9acc90c80ec ("net: virtio_net_hdr_to_skb: count transport header in UFO") while fixing one issue, allowed user space to cook a GSO packet with the following characteristic : IPv4 SKB_GSO_UDP, gso_size=3, skb->len = 28. When this packet arrives in qdisc_pkt_len_init(), we end up with hdr_len = 28 (IPv4 header + UDP header), matching skb->len Then the following sets gso_segs to 0 : gso_segs = DIV_ROUND_UP(skb->len - hdr_len, shinfo->gso_size); Then later we set qdisc_skb_cb(skb)->pkt_len to back to zero :/ qdisc_skb_cb(skb)->pkt_len += (gso_segs - 1) * hdr_len; This leads to the following crash in fq_codel [1] qdisc_pkt_len_init() is best effort, we only want an estimation of the bytes sent on the wire, not crashing the kernel. This patch is fixing this particular issue, a following one adds more sanity checks for another potential bug. [1] [ 70.724101] BUG: kernel NULL pointer dereference, address: 0000000000000000 [ 70.724561] #PF: supervisor read access in kernel mode [ 70.724561] #PF: error_code(0x0000) - not-present page [ 70.724561] PGD 10ac61067 P4D 10ac61067 PUD 107ee2067 PMD 0 [ 70.724561] Oops: Oops: 0000 [#1] SMP NOPTI [ 70.724561] CPU: 11 UID: 0 PID: 2163 Comm: b358537762 Not tainted 6.11.0-virtme #991 [ 70.724561] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [ 70.724561] RIP: 0010:fq_codel_enqueue (net/sched/sch_fq_codel.c:120 net/sched/sch_fq_codel.c:168 net/sched/sch_fq_codel.c:230) sch_fq_codel [ 70.724561] Code: 24 08 49 c1 e1 06 44 89 7c 24 18 45 31 ed 45 31 c0 31 ff 89 44 24 14 4c 03 8b 90 01 00 00 eb 04 39 ca 73 37 4d 8b 39 83 c7 01 <49> 8b 17 49 89 11 41 8b 57 28 45 8b 5f 34 49 c7 07 00 00 00 00 49 All code ======== 0: 24 08 and $0x8,%al 2: 49 c1 e1 06 shl $0x6,%r9 6: 44 89 7c 24 18 mov %r15d,0x18(%rsp) b: 45 31 ed xor %r13d,%r13d e: 45 31 c0 xor %r8d,%r8d 11: 31 ff xor %edi,%edi 13: 89 44 24 14 mov %eax,0x14(%rsp) 17: 4c 03 8b 90 01 00 00 add 0x190(%rbx),%r9 1e: eb 04 jmp 0x24 20: 39 ca cmp %ecx,%edx 22: 73 37 jae 0x5b 24: 4d 8b 39 mov (%r9),%r15 27: 83 c7 01 add $0x1,%edi 2a:* 49 8b 17 mov (%r15),%rdx <-- trapping instruction 2d: 49 89 11 mov %rdx,(%r9) 30: 41 8b 57 28 mov 0x28(%r15),%edx 34: 45 8b 5f 34 mov 0x34(%r15),%r11d 38: 49 c7 07 00 00 00 00 movq $0x0,(%r15) 3f: 49 rex.WB Code starting with the faulting instruction =========================================== 0: 49 8b 17 mov (%r15),%rdx 3: 49 89 11 mov %rdx,(%r9) 6: 41 8b 57 28 mov 0x28(%r15),%edx a: 45 8b 5f 34 mov 0x34(%r15),%r11d e: 49 c7 07 00 00 00 00 movq $0x0,(%r15) 15: 49 rex.WB [ 70.724561] RSP: 0018:ffff95ae85e6fb90 EFLAGS: 00000202 [ 70.724561] RAX: 0000000002000000 RBX: ffff95ae841de000 RCX: 0000000000000000 [ 70.724561] RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000001 [ 70.724561] RBP: ffff95ae85e6fbf8 R08: 0000000000000000 R09: ffff95b710a30000 [ 70.724561] R10: 0000000000000000 R11: bdf289445ce31881 R12: ffff95ae85e6fc58 [ 70.724561] R13: 0000000000000000 R14: 0000000000000040 R15: 0000000000000000 [ 70.724561] FS: 000000002c5c1380(0000) GS:ffff95bd7fcc0000(0000) knlGS:0000000000000000 [ 70.724561] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 70.724561] CR2: 0000000000000000 CR3: 000000010c568000 CR4: 00000000000006f0 [ 70.724561] Call Trace: [ 70.724561] [ 70.724561] ? __die (arch/x86/kernel/dumpstack.c:421 arch/x86/kernel/dumpstack.c:434) [ 70.724561] ? page_fault_oops (arch/x86/mm/fault.c:715) [ 70.724561] ? exc_page_fault (./arch/x86/include/asm/irqflags.h:26 ./arch/x86/include/asm/irqflags.h:87 ./arch/x86/include/asm/irqflags.h:147 arch/x86/mm/fault.c:1489 arch/x86/mm/fault.c:1539) [ 70.724561] ? asm_exc_page_fault (./arch/x86/include/asm/idtentry.h:623) [ 70.724561] ? fq_codel_enqueue (net/sched/sch_fq_codel.c:120 net/sched/sch_fq_codel.c:168 net/sched/sch_fq_codel.c:230) sch_fq_codel [ 70.724561] dev_qdisc_enqueue (net/core/dev.c:3784) [ 70.724561] __dev_queue_xmit (net/core/dev.c:3880 (discriminator 2) net/core/dev.c:4390 (discriminator 2)) [ 70.724561] ? irqentry_enter (kernel/entry/common.c:237) [ 70.724561] ? sysvec_apic_timer_interrupt (./arch/x86/include/asm/hardirq.h:74 (discriminator 2) arch/x86/kernel/apic/apic.c:1043 (discriminator 2) arch/x86/kernel/apic/apic.c:1043 (discriminator 2)) [ 70.724561] ? trace_hardirqs_on (kernel/trace/trace_preemptirq.c:58 (discriminator 4)) [ 70.724561] ? asm_sysvec_apic_timer_interrupt (./arch/x86/include/asm/idtentry.h:702) [ 70.724561] ? virtio_net_hdr_to_skb.constprop.0 (./include/linux/virtio_net.h:129 (discriminator 1)) [ 70.724561] packet_sendmsg (net/packet/af_packet.c:3145 (discriminator 1) net/packet/af_packet.c:3177 (discriminator 1)) [ 70.724561] ? _raw_spin_lock_bh (./arch/x86/include/asm/atomic.h:107 (discriminator 4) ./include/linux/atomic/atomic-arch-fallback.h:2170 (discriminator 4) ./include/linux/atomic/atomic-instrumented.h:1302 (discriminator 4) ./include/asm-generic/qspinlock.h:111 (discriminator 4) ./include/linux/spinlock.h:187 (discriminator 4) ./include/linux/spinlock_api_smp.h:127 (discriminator 4) kernel/locking/spinlock.c:178 (discriminator 4)) [ 70.724561] ? netdev_name_node_lookup_rcu (net/core/dev.c:325 (discriminator 1)) [ 70.724561] __sys_sendto (net/socket.c:730 (discriminator 1) net/socket.c:745 (discriminator 1) net/socket.c:2210 (discriminator 1)) [ 70.724561] ? __sys_setsockopt (./include/linux/file.h:34 net/socket.c:2355) [ 70.724561] __x64_sys_sendto (net/socket.c:2222 (discriminator 1) net/socket.c:2218 (discriminator 1) net/socket.c:2218 (discriminator 1)) [ 70.724561] do_syscall_64 (arch/x86/entry/common.c:52 (discriminator 1) arch/x86/entry/common.c:83 (discriminator 1)) [ 70.724561] entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) [ 70.724561] RIP: 0033:0x41ae09 Fixes: cf9acc90c80ec ("net: virtio_net_hdr_to_skb: count transport header in UFO") Reported-by: syzbot Signed-off-by: Eric Dumazet Cc: Jonathan Davies Reviewed-by: Willem de Bruijn Reviewed-by: Jonathan Davies --- net/core/dev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/core/dev.c b/net/core/dev.c index 1e740faf9e783b047b2dc7d9fd4242e4e6c7317a..f2c47da79f17d5ebe6b334b63d66c84c84c519fc 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -3758,7 +3758,7 @@ static void qdisc_pkt_len_init(struct sk_buff *skb) sizeof(_tcphdr), &_tcphdr); if (likely(th)) hdr_len += __tcp_hdrlen(th); - } else { + } else if (shinfo->gso_type & SKB_GSO_UDP_L4) { struct udphdr _udphdr; if (skb_header_pointer(skb, hdr_len, From patchwork Tue Sep 24 15:02:57 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Dumazet X-Patchwork-Id: 13811011 X-Patchwork-Delegate: kuba@kernel.org Received: from mail-yb1-f202.google.com (mail-yb1-f202.google.com [209.85.219.202]) (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 93C751AB517 for ; Tue, 24 Sep 2024 15:03:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727190186; cv=none; b=CdNjybf2d8dsuqqFVTBurJ496nkOE4mQAodbF4y2vBLIXJLwYStcJPmyhcg2+Z48Lw1K2wEbJKJQLb1vcTjNShje9hdrefOXdzkR8HdE3IGiKfVCFZHLwCi/YJ98E/WYCqDNC5rqBN/NFNLy7UDFXWLJAc2gx0Ie/bN/KZJsofI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727190186; c=relaxed/simple; bh=uH36kzWL1EBdTkFOXHjC/9nsGxPcfD5nMtqJg/GJiuY=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=keTQCWrqijDgVfY60gwajHNgZJL+ozGzn6jWN/Rd08rc5SjdjCHfVa+HD+AzeuQT+M0Ps9ikORSvV8fIIgw1n78VhrvEwxvCVox5cFw0wytSFWMXFXNkCF/zklPXppgif+BgVqZVoaFkIPx5novwq3pGtpADqlLqSAL7GXNnYTU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--edumazet.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=Gc66sG23; arc=none smtp.client-ip=209.85.219.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--edumazet.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="Gc66sG23" Received: by mail-yb1-f202.google.com with SMTP id 3f1490d57ef6-e1ce191f74fso9617368276.2 for ; Tue, 24 Sep 2024 08:03:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1727190183; x=1727794983; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=4Un4IXmB0+ePAT/5m2bLmA+cooZOyhXf430sczYl0HI=; b=Gc66sG23CYRzWlvHHDX3tILXk9bv8LPqkQKvbSY/KVod+H24A8QhrvwwtcrlXQf0bt pwZ5GdeisCy4Mhv92ZVvZsBDzTMh+BYI79kO+MiUK1gBemHZBw5Z5JryALalRz7gQGkw HczCNzEzuBFps8G4NWXaQbDpC8PRhq0EYNp1m6VjlsF/qvd7VaLH9HnPm7DKzlRYTFRM 2hCS69iAg3JRMIWmbC2nYEuvgqB2j96ICRGQwbYxyEbPuCAW6ptJp6gfCVARQUEWEyci AB1V8jPnzD1rtdiysyO9i2yEtbaIZd+M8hG2yn6l+ES2jkT2RI6TH0p/kzCROBhTiXpm glbw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1727190183; x=1727794983; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=4Un4IXmB0+ePAT/5m2bLmA+cooZOyhXf430sczYl0HI=; b=AfRq2XlLYrkOL8fYS8oErmpIhc44Wubu+fCsT52bfvj/U8pKsxSRDWIBZAavHfXlQh TBplZk2aTqmcm5kx4hajl/FaR083XFyS990Y2AudjPPfWw6+EZOdiGlAgAUFRk/eisaN x+30X00VldgZONyuheF8CvAjKFNqUViLqpTUF0YR76nl7TcT3WcyEAUwTWrlWlHzJgRE ZKR3323ASnNwLnNV8GXjEgAE95iZeCes/UlA04vsDtgHVHoIiZb6HMcSv/ZfXVxsXtK8 DoEwSNA3VTaGAA+IFPYKhEmC2AmNNFk8u7n2kJq5iyT+bbXmebp1iXjjC6UcCdihbdnq 4gog== X-Forwarded-Encrypted: i=1; AJvYcCU1ZV4N6C5ACn/nD6SCah1CzVYbbf8GTVqKb/m8mrYz5B4mPxwyzpDUQrFGRYxOFKVLbOOyDFA=@vger.kernel.org X-Gm-Message-State: AOJu0YzZ7OYITwZhuxxxXjzLS/WkaHhaw7QKXqCFmN/rDuqCYClXGRbF 9mmgCxBBLVsJRwpiaHErCAJtnpatjZwR6+fBIIwuBlkyKzuTfnZPB8Xb1lVfMsuDvxum5gsheRU S817yITZuUA== X-Google-Smtp-Source: AGHT+IFblErf3P728ZlcQ1ZStrOT/EGKi6CtIFcve5MnkjFOEHYuMx/u1azvXm4+r3ruRnzFiQqeCEtMJYPukA== X-Received: from edumazet1.c.googlers.com ([fda3:e722:ac3:cc00:f7:ea0b:ac12:11d6]) (user=edumazet job=sendgmr) by 2002:a25:d855:0:b0:e1b:10df:78ea with SMTP id 3f1490d57ef6-e2250c3b7demr11174276.4.1727190183474; Tue, 24 Sep 2024 08:03:03 -0700 (PDT) Date: Tue, 24 Sep 2024 15:02:57 +0000 In-Reply-To: <20240924150257.1059524-1-edumazet@google.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240924150257.1059524-1-edumazet@google.com> X-Mailer: git-send-email 2.46.0.792.g87dc391469-goog Message-ID: <20240924150257.1059524-3-edumazet@google.com> Subject: [PATCH net 2/2] net: add more sanity checks to qdisc_pkt_len_init() From: Eric Dumazet To: "David S . Miller" , Jakub Kicinski , Paolo Abeni Cc: David Ahern , netdev@vger.kernel.org, Willem de Bruijn , Jonathan Davies , eric.dumazet@gmail.com, Eric Dumazet X-Patchwork-Delegate: kuba@kernel.org One path takes care of SKB_GSO_DODGY, assuming skb->len is bigger than hdr_len. virtio_net_hdr_to_skb() does not fully dissect TCP headers, it only make sure it is at least 20 bytes. It is possible for an user to provide a malicious 'GSO' packet, total length of 80 bytes. - 20 bytes of IPv4 header - 60 bytes TCP header - a small gso_size like 8 virtio_net_hdr_to_skb() would declare this packet as a normal GSO packet, because it would see 40 bytes of payload, bigger than gso_size. We need to make detect this case to not underflow qdisc_skb_cb(skb)->pkt_len. Fixes: 1def9238d4aa ("net_sched: more precise pkt_len computation") Signed-off-by: Eric Dumazet Reviewed-by: Willem de Bruijn --- net/core/dev.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/net/core/dev.c b/net/core/dev.c index f2c47da79f17d5ebe6b334b63d66c84c84c519fc..35b8bcfb209bd274c81380eaf6e445641306b018 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -3766,10 +3766,14 @@ static void qdisc_pkt_len_init(struct sk_buff *skb) hdr_len += sizeof(struct udphdr); } - if (shinfo->gso_type & SKB_GSO_DODGY) - gso_segs = DIV_ROUND_UP(skb->len - hdr_len, - shinfo->gso_size); + if (unlikely(shinfo->gso_type & SKB_GSO_DODGY)) { + int payload = skb->len - hdr_len; + /* Malicious packet. */ + if (payload <= 0) + return; + gso_segs = DIV_ROUND_UP(payload, shinfo->gso_size); + } qdisc_skb_cb(skb)->pkt_len += (gso_segs - 1) * hdr_len; } }