Re: [PATCH net] tcp: restrict net.ipv4.tcp_app_win

Kuniyuki Iwashima
2023-04-06T20:40:58Z

From: YueHaibing <yuehaibing@huawei.com>
Date: Thu, 6 Apr 2023 14:34:50 +0800
> UBSAN: shift-out-of-bounds in net/ipv4/tcp_input.c:555:23
> shift exponent 255 is too large for 32-bit type 'int'
> CPU: 1 PID: 7907 Comm: ssh Not tainted 6.3.0-rc4-00161-g62bad54b26db-dirty #206
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
> Call Trace:
> <TASK>
> dump_stack_lvl+0x136/0x150
> __ubsan_handle_shift_out_of_bounds+0x21f/0x5a0
> tcp_init_transfer.cold+0x3a/0xb9
> tcp_finish_connect+0x1d0/0x620
> tcp_rcv_state_process+0xd78/0x4d60
> tcp_v4_do_rcv+0x33d/0x9d0
> __release_sock+0x133/0x3b0
> release_sock+0x58/0x1b0
>
> 'maxwin' is int, shifting int for 32 or more bits is undefined behaviour.
>
> Signed-off-by: YueHaibing <yuehaibing@huawei.com>

Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>

Thanks!

> ---
> Documentation/networking/ip-sysctl.rst | 2 ++
> net/ipv4/sysctl_net_ipv4.c | 3 +++
> 2 files changed, 5 insertions(+)
>
> diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
> index 87dd1c5283e6..58a78a316697 100644
> --- a/Documentation/networking/ip-sysctl.rst
> +++ b/Documentation/networking/ip-sysctl.rst
> @@ -340,6 +340,8 @@ tcp_app_win - INTEGER
> Reserve max(window/2^tcp_app_win, mss) of window for application
> buffer. Value 0 is special, it means that nothing is reserved.
>
> + Possible values are [0, 31], inclusive.
> +
> Default: 31
>
> tcp_autocorking - BOOLEAN
> diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
> index 0d0cc4ef2b85..40fe70fc2015 100644
> --- a/net/ipv4/sysctl_net_ipv4.c
> +++ b/net/ipv4/sysctl_net_ipv4.c
> @@ -25,6 +25,7 @@ static int ip_local_port_range_min[] = { 1, 1 };
> static int ip_local_port_range_max[] = { 65535, 65535 };
> static int tcp_adv_win_scale_min = -31;
> static int tcp_adv_win_scale_max = 31;
> +static int tcp_app_win_max = 31;
> static int tcp_min_snd_mss_min = TCP_MIN_SND_MSS;
> static int tcp_min_snd_mss_max = 65535;
> static int ip_privileged_port_min;
> @@ -1198,6 +1199,8 @@ static struct ctl_table ipv4_net_table[] = {
> .maxlen = sizeof(u8),
> .mode = 0644,
> .proc_handler = proc_dou8vec_minmax,
> + .extra1 = SYSCTL_ZERO,
> + .extra2 = &tcp_app_win_max,
> },
> {
> .procname = "tcp_adv_win_scale",
> --
> 2.34.1