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Message-ID: <86f69e6d3aba5b6a05a79efcf06e575e2dfe9185.camel@mediatek.com>
Date: Tue, 27 May 2025 03:05:06 +0000
From: Shiming Cheng (成诗明)
<Shiming.Cheng@...iatek.com>
To: "davem@...emloft.net" <davem@...emloft.net>, "kuba@...nel.org"
<kuba@...nel.org>, "willemb@...gle.com" <willemb@...gle.com>,
"matthias.bgg@...il.com" <matthias.bgg@...il.com>, "pabeni@...hat.com"
<pabeni@...hat.com>, "willemdebruijn.kernel@...il.com"
<willemdebruijn.kernel@...il.com>, "edumazet@...gle.com"
<edumazet@...gle.com>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
Lena Wang (王娜) <Lena.Wang@...iatek.com>
Subject: Re: [PATCH v2] t: fix udp gso skb_segment after pull from frag_list
On Tue, 2025-05-27 at 10:56 +0800, Shiming Cheng wrote:
> On Mon, 2025-05-26 at 10:41 -0400, Willem de Bruijn wrote:
> > External email : Please do not click links or open attachments
> > until
> > you have verified the sender or the content.
> >
> >
> > s/t/net
> >
> > s/[PATCH vX]/[PATCH net vX]
>
> It has already been updated in v3.
>
> >
> > Shiming Cheng wrote:
> > > Detect invalid geometry due to pull from frag_list, and pass to
> > > regular skb_segment. if only part of the fraglist payload is
> > > pulled
> > > into head_skb, When splitting packets in the skb_segment
> > > function,
> >
> > Punctuation is off
>
> It has already been updated in v3.
>
> >
> > > it will always cause exception as 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.
> > >
> > > When splitting packets in the skb_segment function, the first two
> > > packets of (11,11) bytes are split using skb_copy_bits. But when
> > > the last packet of 10 bytes is split, because hsize becomes
> > > nagative,
> > > it enters the skb_clone process instead of continuing to use
> > > skb_copy_bits. In fact, the data for skb_clone has already been
> > > copied into the second packet.
> > >
> > > when hsize < 0, the payload of the fraglist has already been
> > > copied
> > > (with skb_copy_bits), so there is no need to enter skb_clone to
> > > process this packet. Instead, continue using skb_copy_bits to
> > > process
> > > the next packet.
> >
> > No longer matches the current patch
>
> It has already been updated in v3.
>
> >
> > > BUG_ON here：
> > > pos += skb_headlen(list_skb);
> > > while (pos < offset + len) {
> > > BUG_ON(i >= nfrags);
> > > size = skb_frag_size(frag);
> > >
> > > el1h_64_sync_handler+0x3c/0x90
> > > el1h_64_sync+0x68/0x6c
> > > 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
> > > __do_softirq+0x14/0x20
> > >
> > > [ 118.376811] [C201134] dpmaif_rxq0_pus: [name:bug&]kernel
> > > BUG
> > > at net/core/skbuff.c:4278!
> > > [ 118.376829] [C201134] dpmaif_rxq0_pus:
> > > [name:traps&]Internal
> > > error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP
> > > [ 118.376858] [C201134] dpmaif_rxq0_pus:
> > > [name:mediatek_cpufreq_hw&]cpufreq stop DVFS log done
> > > [ 118.470774] [C201134] dpmaif_rxq0_pus:
> > > [name:mrdump&]Kernel
> > > Offset: 0x178cc00000 from 0xffffffc008000000
> > > [ 118.470810] [C201134] dpmaif_rxq0_pus:
> > > [name:mrdump&]PHYS_OFFSET: 0x40000000
> > > [ 118.470827] [C201134] dpmaif_rxq0_pus:
> > > [name:mrdump&]pstate:
> > > 60400005 (nZCv daif +PAN -UAO)
> > > [ 118.470848] [C201134] dpmaif_rxq0_pus: [name:mrdump&]pc :
> > > [0xffffffd79598aefc] skb_segment+0xcd0/0xd14
> > > [ 118.470900] [C201134] dpmaif_rxq0_pus: [name:mrdump&]lr :
> > > [0xffffffd79598a5e8] skb_segment+0x3bc/0xd14
> > > [ 118.470928] [C201134] dpmaif_rxq0_pus: [name:mrdump&]sp :
> > > ffffffc008013770
> > > [ 118.470941] [C201134] dpmaif_rxq0_pus: [name:mrdump&]x29:
> > > ffffffc008013810 x28: 0000000000000040
> > > [ 118.470961] [C201134] dpmaif_rxq0_pus: [name:mrdump&]x27:
> > > 000000000000002a x26: faffff81338f5500
> > > [ 118.470976] [C201134] dpmaif_rxq0_pus: [name:mrdump&]x25:
> > > f9ffff800c87e000 x24: 0000000000000000
> > > [ 118.470991] [C201134] dpmaif_rxq0_pus: [name:mrdump&]x23:
> > > 000000000000004b x22: f4ffff81338f4c00
> > > [ 118.471005] [C201134] dpmaif_rxq0_pus: [name:mrdump&]x21:
> > > 000000000000000b x20: 0000000000000000
> > > [ 118.471019] [C201134] dpmaif_rxq0_pus: [name:mrdump&]x19:
> > > fdffff8077db5dc8 x18: 0000000000000000
> > > [ 118.471033] [C201134] dpmaif_rxq0_pus: [name:mrdump&]x17:
> > > 00000000ad6b63b6 x16: 00000000ad6b63b6
> > > [ 118.471047] [C201134] dpmaif_rxq0_pus: [name:mrdump&]x15:
> > > ffffffd795aa59d4 x14: ffffffd795aa7bc4
> > > [ 118.471061] [C201134] dpmaif_rxq0_pus: [name:mrdump&]x13:
> > > f4ffff806d40bc00 x12: 0000000100000000
> > > [ 118.471075] [C201134] dpmaif_rxq0_pus: [name:mrdump&]x11:
> > > 0054000800000000 x10: 0000000000000040
> > > [ 118.471089] [C201134] dpmaif_rxq0_pus: [name:mrdump&]x9 :
> > > 0000000000000040 x8 : 0000000000000055
> > > [ 118.471104] [C201134] dpmaif_rxq0_pus: [name:mrdump&]x7 :
> > > ffffffd7959b0868 x6 : ffffffd7959aeebc
> > > [ 118.471118] [C201134] dpmaif_rxq0_pus: [name:mrdump&]x5 :
> > > f8ffff8132ac5720 x4 : ffffffc0080134a8
> > > [ 118.471131] [C201134] dpmaif_rxq0_pus: [name:mrdump&]x3 :
> > > 0000000000000a20 x2 : 0000000000000001
> > > [ 118.471145] [C201134] dpmaif_rxq0_pus: [name:mrdump&]x1 :
> > > 000000000000000a x0 : faffff81338f5500
> >
> > Please truncate to the most relevant information.
>
> It has already been updated in v3.
>
> >
> > That [name:..] stuff looks odd too? Is this normal dmesg? If so,
> > what
> > is the platform.
>
> The device where the issue occurred is Android Mediatek mobile
> platform. Thread and name are related to Mediatek.
The included thread and name log information are likely from the
interrupted thread, this can be seen from the starting irq funtion in
the call stack(__do_softirq+0x14/0x20).
>
>
> >
> > In this case, the (possibly somewhat truncated) stack trace and
> > explicit
> > kernel BUG at statement probably suffice.
> >
> > > Fixes: a1e40ac5b5e9 ("net: gso: fix udp gso fraglist segmentation
> > > after pull from frag_list")
> > > Signed-off-by: Shiming Cheng <shiming.cheng@...iatek.com>
> > > ---
> > > net/ipv4/udp_offload.c | 4 ++++
> > > 1 file changed, 4 insertions(+)
> > >
> > > diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
> > > index a5be6e4ed326..ec05bb7d1e22 100644
> > > --- a/net/ipv4/udp_offload.c
> > > +++ b/net/ipv4/udp_offload.c
> > > @@ -273,6 +273,7 @@ struct sk_buff *__udp_gso_segment(struct
> > > sk_buff *gso_skb,
> > > bool copy_dtor;
> > > __sum16 check;
> > > __be16 newlen;
> > > + int ret = 0;
> > >
> > > mss = skb_shinfo(gso_skb)->gso_size;
> > > if (gso_skb->len <= sizeof(*uh) + mss)
> > > @@ -301,6 +302,9 @@ struct sk_buff *__udp_gso_segment(struct
> > > sk_buff *gso_skb,
> > > if (skb_pagelen(gso_skb) - sizeof(*uh) ==
> > > skb_shinfo(gso_skb)->gso_size)
> > > return __udp_gso_segment_list(gso_skb,
> > > features, is_ipv6);
> > >
> > > + ret = __skb_linearize(gso_skb);
> > > + if (ret)
> > > + return ERR_PTR(ret);
> >
> > code LGTM, thanks.
> >
> > > /* Setup csum, as fraglist skips this in
> > > udp4_gro_receive. */
> > > gso_skb->csum_start = skb_transport_header(gso_skb)
> > > -
> > > gso_skb->head;
> > > gso_skb->csum_offset = offsetof(struct udphdr,
> > > check);
> > > --
> > > 2.45.2
> > >
> >
> >
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