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Message-ID: <c94c939ffe846c7f86daaddaef8661cdfe3f0b8f.camel@kernel.org>
Date: Wed, 26 Jun 2024 21:05:44 +0800
From: Geliang Tang <geliang@...nel.org>
To: John Fastabend <john.fastabend@...il.com>
Cc: Jakub Sitnicki <jakub@...udflare.com>, "David S. Miller"
<davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
<pabeni@...hat.com>, David Ahern <dsahern@...nel.org>, Andrii Nakryiko
<andrii@...nel.org>, Eduard Zingerman <eddyz87@...il.com>, Mykola Lysenko
<mykolal@...com>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann
<daniel@...earbox.net>, Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu
<song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>, KP Singh
<kpsingh@...nel.org>, Stanislav Fomichev <sdf@...gle.com>, Eric Dumazet
<edumazet@...gle.com>, Hao Luo <haoluo@...gle.com>, Jiri Olsa
<jolsa@...nel.org>, Shuah Khan <shuah@...nel.org>, Mykyta Yatsenko
<yatsenko@...a.com>, Miao Xu <miaxu@...a.com>, Yuran Pereira
<yuran.pereira@...mail.com>, Huacai Chen <chenhuacai@...nel.org>, Tiezhu
Yang <yangtiezhu@...ngson.cn>, Geliang Tang <tanggeliang@...inos.cn>,
netdev@...r.kernel.org, bpf@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH bpf-next v2 1/4] skmsg: null check for sg_page in
sk_msg_recvmsg
On Tue, 2024-06-25 at 12:37 -0700, John Fastabend wrote:
> Eric Dumazet wrote:
> > On Tue, Jun 25, 2024 at 10:25 AM Geliang Tang <geliang@...nel.org>
> > wrote:
> > >
> > > From: Geliang Tang <tanggeliang@...inos.cn>
> > >
> > > Run the following BPF selftests on Loongarch:
> > >
> > > ./test_progs -t sockmap_basic
> > >
> > > A Kernel panic occurs:
> > >
> > > '''
> > > Oops[#1]:
> > > CPU: 22 PID: 2824 Comm: test_progs Tainted: G OE
> > > 6.10.0-rc2+ #18
> > > Hardware name: LOONGSON Dabieshan/Loongson-TC542F0, BIOS
> > > Loongson-UDK2018-V4.0.11
> > > pc 9000000004162774 ra 90000000048bf6c0 tp 90001000aa16c000 sp
> > > 90001000aa16fb90
> > > a0 0000000000000000 a1 0000000000000000 a2 0000000000000000 a3
> > > 90001000aa16fd70
> > > a4 0000000000000800 a5 0000000000000000 a6 000055557b63aae8 a7
> > > 00000000000000cf
> > > t0 0000000000000000 t1 0000000000004000 t2 0000000000000048 t3
> > > 0000000000000000
> > > t4 0000000000000001 t5 0000000000000002 t6 0000000000000001 t7
> > > 0000000000000002
> > > t8 0000000000000018 u0 9000000004856150 s9 0000000000000000 s0
> > > 0000000000000000
> > > s1 0000000000000000 s2 90001000aa16fd70 s3 0000000000000000 s4
> > > 0000000000000000
> > > s5 0000000000004000 s6 900010009284dc00 s7 0000000000000001 s8
> > > 900010009284dc00
> > > ra: 90000000048bf6c0 sk_msg_recvmsg+0x120/0x560
> > > ERA: 9000000004162774 copy_page_to_iter+0x74/0x1c0
> > > CRMD: 000000b0 (PLV0 -IE -DA +PG DACF=CC DACM=CC -WE)
> > > PRMD: 0000000c (PPLV0 +PIE +PWE)
> > > EUEN: 00000007 (+FPE +SXE +ASXE -BTE)
> > > ECFG: 00071c1d (LIE=0,2-4,10-12 VS=7)
> > > ESTAT: 00010000 [PIL] (IS= ECode=1 EsubCode=0)
> > > BADV: 0000000000000040
> > > PRID: 0014c011 (Loongson-64bit, Loongson-3C5000)
> > > Modules linked in: bpf_testmod(OE) xt_CHECKSUM xt_MASQUERADE
> > > xt_conntrack
> > > Process test_progs (pid: 2824, threadinfo=0000000000863a31,
> > > task=000000001cba0874)
> > > Stack : 0000000000000001 fffffffffffffffc 0000000000000000
> > > 0000000000000000
> > > 0000000000000018 0000000000000000 0000000000000000
> > > 90000000048bf6c0
> > > 90000000052cd638 90001000aa16fd70 900010008bf51580
> > > 900010009284f000
> > > 90000000049f2b90 900010009284f188 900010009284f178
> > > 90001000861d4780
> > > 9000100084dccd00 0000000000000800 0000000000000007
> > > fffffffffffffff2
> > > 000000000453e92f 90000000049aae34 90001000aa16fd60
> > > 900010009284f000
> > > 0000000000000000 0000000000000000 900010008bf51580
> > > 90000000049f2b90
> > > 0000000000000001 0000000000000000 9000100084dc3a10
> > > 900010009284f1ac
> > > 90001000aa16fd40 0000555559953278 0000000000000001
> > > 0000000000000000
> > > 90001000aa16fdc8 9000000005a5a000 90001000861d4780
> > > 0000000000000800
> > > ...
> > > Call Trace:
> > > [<9000000004162774>] copy_page_to_iter+0x74/0x1c0
> > > [<90000000048bf6c0>] sk_msg_recvmsg+0x120/0x560
> > > [<90000000049f2b90>] tcp_bpf_recvmsg_parser+0x170/0x4e0
> > > [<90000000049aae34>] inet_recvmsg+0x54/0x100
> > > [<900000000481ad5c>] sock_recvmsg+0x7c/0xe0
> > > [<900000000481e1a8>] __sys_recvfrom+0x108/0x1c0
> > > [<900000000481e27c>] sys_recvfrom+0x1c/0x40
> > > [<9000000004c076ec>] do_syscall+0x8c/0xc0
> > > [<9000000003731da4>] handle_syscall+0xc4/0x160
> > >
> > > Code: 0010b09b 440125a0 0011df8d <28c10364> 0012b70c
> > > 00133305 0013b1ac 0010dc84 00151585
> > >
> > > ---[ end trace 0000000000000000 ]---
> > > Kernel panic - not syncing: Fatal exception
> > > Kernel relocated by 0x3510000
> > > .text @ 0x9000000003710000
> > > .data @ 0x9000000004d70000
> > > .bss @ 0x9000000006469400
> > > ---[ end Kernel panic - not syncing: Fatal exception ]---
> > > '''
> > >
> > > This is because "sg_page(sge)" is NULL in that case. This patch
> > > adds null
> > > check for it in sk_msg_recvmsg() to fix this error.
> > >
> > > Fixes: 604326b41a6f ("bpf, sockmap: convert to generic sk_msg
> > > interface")
> > > Signed-off-by: Geliang Tang <tanggeliang@...inos.cn>
> > > ---
> > > net/core/skmsg.c | 2 ++
> > > 1 file changed, 2 insertions(+)
> > >
> > > diff --git a/net/core/skmsg.c b/net/core/skmsg.c
> > > index fd20aae30be2..bafcc1e2eadf 100644
> > > --- a/net/core/skmsg.c
> > > +++ b/net/core/skmsg.c
> > > @@ -432,6 +432,8 @@ int sk_msg_recvmsg(struct sock *sk, struct
> > > sk_psock *psock, struct msghdr *msg,
> > > sge = sk_msg_elem(msg_rx, i);
> > > copy = sge->length;
> > > page = sg_page(sge);
> > > + if (!page)
> > > + goto out;
> > > if (copied + copy > len)
> > > copy = len - copied;
> > > copy = copy_page_to_iter(page, sge-
> > > >offset, copy, iter);
> > > --
> > > 2.43.0
> > >
> >
> > This looks pretty much random to me.
> >
> > Please find the root cause, instead of desperately trying to fix
> > 'tests'.
>
> If this happens then either we put a bad msg_rx on the queue see a
> few lines
> up and we need to sort out why that msg_rx was built. Or we walked
> off the
> end of a scatter gather list and need to see why this test isn't
> sufficient?
>
> } while ((i != msg_rx->sg.end) && !sg_is_last(sge))
>
> is this happening every time you run the command or did you run this
> for
> a long iteration and eventually hit this? I don't see why this would
> be
This happens every time when run test_sockmap_skb_verdict_shutdown test
in sockmap_basic. It hits this null page case on X86_64 platform too.
> specific to your arch though.
Kernel panics when a null page is passed to kmap_local_page() on
Loongarch only, and this function is an arch specific one. I think this
issue is somehow related to Loongarch's memory management.
Thanks,
-Geliang
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