netdev - Re: [PATCH net] net_sched: sch_fq: better validate TCA_FQ_WEIGHTS and TCA_FQ

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Date: Tue, 7 Nov 2023 17:59:54 -0500
From: Jamal Hadi Salim <jhs@...atatu.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Willem de Bruijn <willemb@...gle.com>, 
	Cong Wang <xiyou.wangcong@...il.com>, Toke Høiland-Jørgensen <toke@...hat.com>, 
	Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	syzbot <syzkaller@...glegroups.com>
Subject: Re: [PATCH net] net_sched: sch_fq: better validate TCA_FQ_WEIGHTS and TCA_FQ_PRIOMAP

On Tue, Nov 7, 2023 at 11:04 AM Eric Dumazet <edumazet@...gle.com> wrote:
>
> syzbot was able to trigger the following report while providing
> too small TCA_FQ_WEIGHTS attribute [1]
>
> Fix is to use NLA_POLICY_EXACT_LEN() to ensure user space
> provided correct sizes.
>
> Apply the same fix to TCA_FQ_PRIOMAP.
>
> [1]
> BUG: KMSAN: uninit-value in fq_load_weights net/sched/sch_fq.c:960 [inline]
> BUG: KMSAN: uninit-value in fq_change+0x1348/0x2fe0 net/sched/sch_fq.c:1071
> fq_load_weights net/sched/sch_fq.c:960 [inline]
> fq_change+0x1348/0x2fe0 net/sched/sch_fq.c:1071
> fq_init+0x68e/0x780 net/sched/sch_fq.c:1159
> qdisc_create+0x12f3/0x1be0 net/sched/sch_api.c:1326
> tc_modify_qdisc+0x11ef/0x2c20
> rtnetlink_rcv_msg+0x16a6/0x1840 net/core/rtnetlink.c:6558
> netlink_rcv_skb+0x371/0x650 net/netlink/af_netlink.c:2545
> rtnetlink_rcv+0x34/0x40 net/core/rtnetlink.c:6576
> netlink_unicast_kernel net/netlink/af_netlink.c:1342 [inline]
> netlink_unicast+0xf47/0x1250 net/netlink/af_netlink.c:1368
> netlink_sendmsg+0x1238/0x13d0 net/netlink/af_netlink.c:1910
> sock_sendmsg_nosec net/socket.c:730 [inline]
> __sock_sendmsg net/socket.c:745 [inline]
> ____sys_sendmsg+0x9c2/0xd60 net/socket.c:2588
> ___sys_sendmsg+0x28d/0x3c0 net/socket.c:2642
> __sys_sendmsg net/socket.c:2671 [inline]
> __do_sys_sendmsg net/socket.c:2680 [inline]
> __se_sys_sendmsg net/socket.c:2678 [inline]
> __x64_sys_sendmsg+0x307/0x490 net/socket.c:2678
> do_syscall_x64 arch/x86/entry/common.c:51 [inline]
> do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
> entry_SYSCALL_64_after_hwframe+0x63/0x6b
>
> Uninit was created at:
> slab_post_alloc_hook+0x129/0xa70 mm/slab.h:768
> slab_alloc_node mm/slub.c:3478 [inline]
> kmem_cache_alloc_node+0x5e9/0xb10 mm/slub.c:3523
> kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:560
> __alloc_skb+0x318/0x740 net/core/skbuff.c:651
> alloc_skb include/linux/skbuff.h:1286 [inline]
> netlink_alloc_large_skb net/netlink/af_netlink.c:1214 [inline]
> netlink_sendmsg+0xb34/0x13d0 net/netlink/af_netlink.c:1885
> sock_sendmsg_nosec net/socket.c:730 [inline]
> __sock_sendmsg net/socket.c:745 [inline]
> ____sys_sendmsg+0x9c2/0xd60 net/socket.c:2588
> ___sys_sendmsg+0x28d/0x3c0 net/socket.c:2642
> __sys_sendmsg net/socket.c:2671 [inline]
> __do_sys_sendmsg net/socket.c:2680 [inline]
> __se_sys_sendmsg net/socket.c:2678 [inline]
> __x64_sys_sendmsg+0x307/0x490 net/socket.c:2678
> do_syscall_x64 arch/x86/entry/common.c:51 [inline]
> do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
> entry_SYSCALL_64_after_hwframe+0x63/0x6b
>
> CPU: 1 PID: 5001 Comm: syz-executor300 Not tainted 6.6.0-syzkaller-12401-g8f6f76a6a29f #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023
>
> Fixes: 29f834aa326e ("net_sched: sch_fq: add 3 bands and WRR scheduling")
> Fixes: 49e7265fd098 ("net_sched: sch_fq: add TCA_FQ_WEIGHTS attribute")
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> ---
>  net/sched/sch_fq.c | 10 ++--------
>  1 file changed, 2 insertions(+), 8 deletions(-)
>
> diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c
> index 0fd18c344ab5ae6d53e12fc764c0506a2979b4c8..3a31c47fea9bd97d815f2624d926bf7be62387cd 100644
> --- a/net/sched/sch_fq.c
> +++ b/net/sched/sch_fq.c
> @@ -919,14 +919,8 @@ static const struct nla_policy fq_policy[TCA_FQ_MAX + 1] = {
>         [TCA_FQ_TIMER_SLACK]            = { .type = NLA_U32 },
>         [TCA_FQ_HORIZON]                = { .type = NLA_U32 },
>         [TCA_FQ_HORIZON_DROP]           = { .type = NLA_U8 },
> -       [TCA_FQ_PRIOMAP]                = {
> -                       .type = NLA_BINARY,
> -                       .len = sizeof(struct tc_prio_qopt),
> -               },
> -       [TCA_FQ_WEIGHTS]                = {
> -                       .type = NLA_BINARY,
> -                       .len = FQ_BANDS * sizeof(s32),
> -               },
> +       [TCA_FQ_PRIOMAP]                = NLA_POLICY_EXACT_LEN(sizeof(struct tc_prio_qopt)),
> +       [TCA_FQ_WEIGHTS]                = NLA_POLICY_EXACT_LEN(FQ_BANDS * sizeof(s32)),
>  };
>
>  /* compress a u8 array with all elems <= 3 to an array of 2-bit fields */

Acked-by: Jamal Hadi Salim<jhs@...atatu.com>

cheers,
jamal
> --
> 2.42.0.869.gea05f2083d-goog
>