netdev - Re: [PATCH net v3 1/2] skmsg: prevent empty ingress skb from enqueuing

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Message-ID: <b2fb15b791c27d8a76d87d759e9de838af233ee8.camel@kernel.org>
Date: Tue, 02 Jul 2024 15:02:17 +0800
From: Geliang Tang <geliang@...nel.org>
To: John Fastabend <john.fastabend@...il.com>, Jakub Sitnicki
 <jakub@...udflare.com>, "David S. Miller" <davem@...emloft.net>, Eric
 Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo
 Abeni <pabeni@...hat.com>, Alexei Starovoitov <ast@...nel.org>, Daniel
 Borkmann <daniel@...earbox.net>
Cc: "D. Wythe" <alibuda@...ux.alibaba.com>, Geliang Tang
 <tanggeliang@...inos.cn>, David Ahern <dsahern@...nel.org>, Eduard
 Zingerman <eddyz87@...il.com>, Mykola Lysenko <mykolal@...com>, 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>, netdev@...r.kernel.org, bpf@...r.kernel.org,
  linux-kselftest@...r.kernel.org
Subject: Re: [PATCH net v3 1/2] skmsg: prevent empty ingress skb from
 enqueuing

Superseded.

I just sent a v4 ("skmsg: skip empty sge in sk_msg_recvmsg").

Thanks,
-Geliang

On Fri, 2024-06-28 at 13:47 +0800, Geliang Tang wrote:
> From: Geliang Tang <tanggeliang@...inos.cn>
> 
> Run this BPF selftests (./test_progs -t sockmap_basic) on a Loongarch
> platform, 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
>    ... ...
>    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=...)
> Stack : ...
>         ...
> 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: ...
> 
> ---[ 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 crash happens every time when running
> sockmap_skb_verdict_shutdown
> subtest in sockmap_basic.
> 
> This crash is because a NULL pointer is passed to page_address() in
> sk_msg_recvmsg(). Due to the difference in architecture,
> page_address(0)
> will not trigger a panic on the X86 platform but will panic on the
> Loogarch platform. So this bug was hidden on the x86 platform, but
> now
> it is exposed on the Loogarch platform.
> 
> The root cause is an empty skb (skb->len == 0) is put on the queue.
> 
> In this case, in sk_psock_skb_ingress_enqueue(), num_sge is zero, and
> no
> page is put to this sge (see sg_set_page in sg_set_page), but this
> empty
> sge is queued into ingress_msg list.
> 
> And in sk_msg_recvmsg(), this empty sge is used, and a NULL page is
> got by sg_page(sge). Pass this NULL-page to copy_page_to_iter(), it
> passed to kmap_local_page() and page_address(), then kernel panics.
> 
> To solve this, we should prevent empty skb from putting on the queue.
> So
> in sk_psock_verdict_recv(), if the skb->len is zero, drop this skb.
> 
> Fixes: ef5659280eb1 ("bpf, sockmap: Allow skipping sk_skb parser
> program")
> Signed-off-by: Geliang Tang <tanggeliang@...inos.cn>
> ---
>  net/core/skmsg.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/core/skmsg.c b/net/core/skmsg.c
> index fd20aae30be2..44952cdd1425 100644
> --- a/net/core/skmsg.c
> +++ b/net/core/skmsg.c
> @@ -1184,7 +1184,7 @@ static int sk_psock_verdict_recv(struct sock
> *sk, struct sk_buff *skb)
>  
>  	rcu_read_lock();
>  	psock = sk_psock(sk);
> -	if (unlikely(!psock)) {
> +	if (unlikely(!psock || !len)) {
>  		len = 0;
>  		tcp_eat_skb(sk, skb);
>  		sock_drop(sk, skb);