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Date: Tue, 25 Jun 2024 12:37:39 -0700
From: John Fastabend <john.fastabend@...il.com>
To: Eric Dumazet <edumazet@...gle.com>,
Geliang Tang <geliang@...nel.org>
Cc: John Fastabend <john.fastabend@...il.com>,
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>,
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
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
specific to your arch though.
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