netdev - Re: [PATCH net] net_sched: reject silly cell_log in qdisc_get

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Date:   Thu, 14 Jan 2021 10:03:39 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        syzbot <syzkaller@...glegroups.com>
Subject: Re: [PATCH net] net_sched: reject silly cell_log in qdisc_get_rtab()

On Thu, Jan 14, 2021 at 8:06 AM Eric Dumazet <eric.dumazet@...il.com> wrote:
>
> From: Eric Dumazet <edumazet@...gle.com>
>
> iproute2 probably never goes beyond 8 for the cell exponent,
> but stick to the max shift exponent for signed 32bit.
>
> UBSAN reported:
> UBSAN: shift-out-of-bounds in net/sched/sch_api.c:389:22
> shift exponent 130 is too large for 32-bit type 'int'
> CPU: 1 PID: 8450 Comm: syz-executor586 Not tainted 5.11.0-rc3-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:79 [inline]
>  dump_stack+0x183/0x22e lib/dump_stack.c:120
>  ubsan_epilogue lib/ubsan.c:148 [inline]
>  __ubsan_handle_shift_out_of_bounds+0x432/0x4d0 lib/ubsan.c:395
>  __detect_linklayer+0x2a9/0x330 net/sched/sch_api.c:389
>  qdisc_get_rtab+0x2b5/0x410 net/sched/sch_api.c:435
>  cbq_init+0x28f/0x12c0 net/sched/sch_cbq.c:1180
>  qdisc_create+0x801/0x1470 net/sched/sch_api.c:1246
>  tc_modify_qdisc+0x9e3/0x1fc0 net/sched/sch_api.c:1662
>  rtnetlink_rcv_msg+0xb1d/0xe60 net/core/rtnetlink.c:5564
>  netlink_rcv_skb+0x1f0/0x460 net/netlink/af_netlink.c:2494
>  netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
>  netlink_unicast+0x7de/0x9b0 net/netlink/af_netlink.c:1330
>  netlink_sendmsg+0xaa6/0xe90 net/netlink/af_netlink.c:1919
>  sock_sendmsg_nosec net/socket.c:652 [inline]
>  sock_sendmsg net/socket.c:672 [inline]
>  ____sys_sendmsg+0x5a2/0x900 net/socket.c:2345
>  ___sys_sendmsg net/socket.c:2399 [inline]
>  __sys_sendmsg+0x319/0x400 net/socket.c:2432
>  do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: syzbot <syzkaller@...glegroups.com>

Acked-by: Cong Wang <cong.wang@...edance.com>

Thanks.