From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E2BEC226CF4; Thu, 29 May 2025 10:28:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748514498; cv=none; b=WOHfIwCsIKfQm599cBUWc60k9aKTQZReiab3V1zXx3ATCItfahu4bPfUcjS3OsV4gifh4T3RBbu9MReVA0Cb68g049ZO0GAdaothfYflQn01RvLFkQVqSfc9wOWXOZnhV2e/KHTUZuFyDwpJ2QSFMC2p2uLdqgMziFrIgZIcf0E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748514498; c=relaxed/simple; bh=oZNH2VSpnTfpJCZrWcUJQiqZm62W1HZxvQPvid5zsBg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=VWHVftE3twwTgkTKfQ9Crhb302To1TBCAKpFPxOh/RHsFLiBXzSRPWUmwKwLE+ke0h7z7MYugJq9QJ/4UYcCH6BoKGrtI4azKpaHvcRdxPosvJ7EW3DoQVQq5vk0h2jNaO+nv+5F9rAE/L1EDPFI8M7J+qIByeRF9FoO1FjLlH4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=tYgZ1oot; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="tYgZ1oot" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B0F72C4CEE7; Thu, 29 May 2025 10:28:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1748514497; bh=oZNH2VSpnTfpJCZrWcUJQiqZm62W1HZxvQPvid5zsBg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=tYgZ1ootQs40l8ImVx808zn3WUPRC6a8TjUMe76HuYjcg42e1MPKuU/riTGBLf1hS 2MwS714D5CikiGXmHpz17CPWLM39Q5JWxe4CJIknDQGT/5tx8Zoccq3Ktblv57cj7D MlNxScsyLmam0JbzTT4YW8V/KGwtM0mJk7Z3ruV//yRESIYs6GRwmsBdk4Jo0l4cmX 6MxLmPJl8So6vK6IioztPMB9035j34KXG43RwcF2HUYJ4z+PRu2FmwrJyS+vHXu9gH 62cz1PPWsytgNUpTngAhhgVy0PSfGXSchTC3AU2x21AlsVKb1Ju4J/Y58txBdwhhh2 Axy3C6gIl4FxA== Date: Thu, 29 May 2025 11:28:12 +0100 From: Simon Horman To: Shiming Cheng Cc: willemdebruijn.kernel@gmail.com, willemb@google.com, edumazet@google.com, davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com, matthias.bgg@gmail.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, lena.wang@mediatek.com Subject: Re: [PATCH net v5] net: fix udp gso skb_segment after pull from frag_list Message-ID: <20250529102812.GL1484967@horms.kernel.org> References: <20250529015901.3814-1-shiming.cheng@mediatek.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250529015901.3814-1-shiming.cheng@mediatek.com> On Thu, May 29, 2025 at 09:58:56AM +0800, Shiming Cheng wrote: > Commit a1e40ac5b5e9 ("net: gso: fix udp gso fraglist segmentation after > pull from frag_list") detected invalid geometry in frag_list skbs and > redirects them from skb_segment_list to more robust skb_segment. But some > packets with modified geometry can also hit bugs in that code. We don't > know how many such cases exist. Addressing each one by one also requires > touching the complex skb_segment code, which risks introducing bugs for > other types of skbs. Instead, linearize all these packets that fail the > basic invariants on gso fraglist skbs. That is more robust. > > If only part of the fraglist payload is pulled into head_skb, it will > always cause exception when splitting skbs by skb_segment. For detailed > call stack information, see below. > > Valid SKB_GSO_FRAGLIST skbs > - consist of two or more segments > - the head_skb holds the protocol headers plus first gso_size > - one or more frag_list skbs hold exactly one segment > - all but the last must be gso_size > > Optional datapath hooks such as NAT and BPF (bpf_skb_pull_data) can > modify fraglist skbs, breaking these invariants. > > In extreme cases they pull one part of data into skb linear. For UDP, > this causes three payloads with lengths of (11,11,10) bytes were > pulled tail to become (12,10,10) bytes. > > The skbs no longer meets the above SKB_GSO_FRAGLIST conditions because > payload was pulled into head_skb, it needs to be linearized before pass > to regular skb_segment. > > skb_segment+0xcd0/0xd14 > __udp_gso_segment+0x334/0x5f4 > udp4_ufo_fragment+0x118/0x15c > inet_gso_segment+0x164/0x338 > skb_mac_gso_segment+0xc4/0x13c > __skb_gso_segment+0xc4/0x124 > validate_xmit_skb+0x9c/0x2c0 > validate_xmit_skb_list+0x4c/0x80 > sch_direct_xmit+0x70/0x404 > __dev_queue_xmit+0x64c/0xe5c > neigh_resolve_output+0x178/0x1c4 > ip_finish_output2+0x37c/0x47c > __ip_finish_output+0x194/0x240 > ip_finish_output+0x20/0xf4 > ip_output+0x100/0x1a0 > NF_HOOK+0xc4/0x16c > ip_forward+0x314/0x32c > ip_rcv+0x90/0x118 > __netif_receive_skb+0x74/0x124 > process_backlog+0xe8/0x1a4 > __napi_poll+0x5c/0x1f8 > net_rx_action+0x154/0x314 > handle_softirqs+0x154/0x4b8 > > [118.376811] [C201134] rxq0_pus: [name:bug&]kernel BUG at net/core/skbuff.c:4278! > [118.376829] [C201134] rxq0_pus: [name:traps&]Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP > [118.470774] [C201134] rxq0_pus: [name:mrdump&]Kernel Offset: 0x178cc00000 from 0xffffffc008000000 > [118.470810] [C201134] rxq0_pus: [name:mrdump&]PHYS_OFFSET: 0x40000000 > [118.470827] [C201134] rxq0_pus: [name:mrdump&]pstate: 60400005 (nZCv daif +PAN -UAO) > [118.470848] [C201134] rxq0_pus: [name:mrdump&]pc : [0xffffffd79598aefc] skb_segment+0xcd0/0xd14 > [118.470900] [C201134] rxq0_pus: [name:mrdump&]lr : [0xffffffd79598a5e8] skb_segment+0x3bc/0xd14 > [118.470928] [C201134] rxq0_pus: [name:mrdump&]sp : ffffffc008013770 > > Fixes: a1e40ac5b5e9 ("net: gso: fix udp gso fraglist segmentation after pull from frag_list") nit: This may not be important, but I believe that "net :" doesn't appear in the subject of the cited patch in git history. That is, I think this should be: Fixes: a1e40ac5b5e9 ("gso: fix udp gso fraglist segmentation after pull from frag_list") > Signed-off-by: Shiming Cheng ...