RE: [PATCH] bpf/sockmap: fix kernel panic at __tcp_bpf_recvmsg

From: John Fastabend <john.fastabend@gmail.com>
To: dihu <anny.hu@linux.alibaba.com>, bpf@vger.kernel.org
Cc: netdev@vger.kernel.org, dihu <anny.hu@linux.alibaba.com>
Subject: RE: [PATCH] bpf/sockmap: fix kernel panic at __tcp_bpf_recvmsg
Date: Mon, 08 Jun 2020 09:06:27 -0700	[thread overview]
Message-ID: <5ede6203aba1d_2c272afa690ca5c4c6@john-XPS-13-9370.notmuch> (raw)
In-Reply-To: <20200605084625.9783-1-anny.hu@linux.alibaba.com>

dihu wrote:
> When user application calls read() with MSG_PEEK flag to read data
> of bpf sockmap socket, kernel panic happens at
> __tcp_bpf_recvmsg+0x12c/0x350. sk_msg is not removed from ingress_msg
> queue after read out under MSG_PEEK flag is set. Because it's not
> judged whether sk_msg is the last msg of ingress_msg queue, the next
> sk_msg may be the head of ingress_msg queue, whose memory address of
> sg page is invalid. So it's necessary to add check codes to prevent
> this problem.
> 
> [20759.125457] BUG: kernel NULL pointer dereference, address:
> 0000000000000008
> [20759.132118] CPU: 53 PID: 51378 Comm: envoy Tainted: G            E
> 5.4.32 #1
> [20759.140890] Hardware name: Inspur SA5212M4/YZMB-00370-109, BIOS
> 4.1.12 06/18/2017
> [20759.149734] RIP: 0010:copy_page_to_iter+0xad/0x300
> [20759.270877] __tcp_bpf_recvmsg+0x12c/0x350
> [20759.276099] tcp_bpf_recvmsg+0x113/0x370
> [20759.281137] inet_recvmsg+0x55/0xc0
> [20759.285734] __sys_recvfrom+0xc8/0x130
> [20759.290566] ? __audit_syscall_entry+0x103/0x130
> [20759.296227] ? syscall_trace_enter+0x1d2/0x2d0
> [20759.301700] ? __audit_syscall_exit+0x1e4/0x290
> [20759.307235] __x64_sys_recvfrom+0x24/0x30
> [20759.312226] do_syscall_64+0x55/0x1b0
> [20759.316852] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 
> Signed-off-by: dihu <anny.hu@linux.alibaba.com>
> ---
>  net/ipv4/tcp_bpf.c | 3 +++
>  1 file changed, 3 insertions(+)
> 

Thanks, looks good to me.

Acked-by: John Fastabend <john.fastabend@gmail.com>