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Message-ID: <CAM0EoMkrpShprVbWSFN3FpFWtK9494Hyo+mOSNOJmXCFoieN7Q@mail.gmail.com> Date: Sun, 28 May 2023 15:05:02 -0400 From: Jamal Hadi Salim <jhs@...atatu.com> To: Zhengchao Shao <shaozhengchao@...wei.com> Cc: netdev@...r.kernel.org, xiyou.wangcong@...il.com, jiri@...nulli.us, davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, weiyongjun1@...wei.com, yuehaibing@...wei.com, wanghai38@...wei.com, Peilin Ye <yepeilin.cs@...il.com> Subject: Re: [PATCH net] net: sched: fix NULL pointer dereference in mq_attach On Sat, May 27, 2023 at 5:30 AM Zhengchao Shao <shaozhengchao@...wei.com> wrote: > > When use the following command to test: > 1)ip link add bond0 type bond > 2)ip link set bond0 up > 3)tc qdisc add dev bond0 root handle ffff: mq > 4)tc qdisc replace dev bond0 parent ffff:fff1 handle ffff: mq > This is fixed by Peilin in this ongoing discussion: https://lore.kernel.org/netdev/cover.1684887977.git.peilin.ye@bytedance.com/ cheers, jamal > The kernel reports NULL pointer dereference issue. The stack information > is as follows: > Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 > Internal error: Oops: 0000000096000006 [#1] SMP > Modules linked in: > pstate: 20000005 (nzCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) > pc : mq_attach+0x44/0xa0 > lr : qdisc_graft+0x20c/0x5cc > sp : ffff80000e2236a0 > x29: ffff80000e2236a0 x28: ffff0000c0e59d80 x27: ffff0000c0be19c0 > x26: ffff0000cae3e800 x25: 0000000000000010 x24: 00000000fffffff1 > x23: 0000000000000000 x22: ffff0000cae3e800 x21: ffff0000c9df4000 > x20: ffff0000c9df4000 x19: 0000000000000000 x18: ffff80000a934000 > x17: ffff8000f5b56000 x16: ffff80000bb08000 x15: 0000000000000000 > x14: 0000000000000000 x13: 6b6b6b6b6b6b6b6b x12: 6b6b6b6b00000001 > x11: 0000000000000000 x10: 0000000000000000 x9 : 0000000000000000 > x8 : ffff0000c0be0730 x7 : bbbbbbbbbbbbbbbb x6 : 0000000000000008 > x5 : ffff0000cae3e864 x4 : 0000000000000000 x3 : 0000000000000001 > x2 : 0000000000000001 x1 : ffff8000090bc23c x0 : 0000000000000000 > Call trace: > mq_attach+0x44/0xa0 > qdisc_graft+0x20c/0x5cc > tc_modify_qdisc+0x1c4/0x664 > rtnetlink_rcv_msg+0x354/0x440 > netlink_rcv_skb+0x64/0x144 > rtnetlink_rcv+0x28/0x34 > netlink_unicast+0x1e8/0x2a4 > netlink_sendmsg+0x308/0x4a0 > sock_sendmsg+0x64/0xac > ____sys_sendmsg+0x29c/0x358 > ___sys_sendmsg+0x90/0xd0 > __sys_sendmsg+0x7c/0xd0 > __arm64_sys_sendmsg+0x2c/0x38 > invoke_syscall+0x54/0x114 > el0_svc_common.constprop.1+0x90/0x174 > do_el0_svc+0x3c/0xb0 > el0_svc+0x24/0xec > el0t_64_sync_handler+0x90/0xb4 > el0t_64_sync+0x174/0x178 > > This is because when mq is added for the first time, qdiscs in mq is set > to NULL in mq_attach(). Therefore, when replacing mq after adding mq, we > need to initialize qdiscs in the mq before continuing to graft. Otherwise, > it will couse NULL pointer dereference issue in mq_attach(). And the same > issue will occur in the attach functions of mqprio, taprio and htb. > ffff:fff1 means that the repalce qdisc is ingress. Ingress does not allow > any qdisc to be attached. Therefore, ffff:fff1 is incorrectly used, and > the command should be dropped. > > Fixes: 6ec1c69a8f64 ("net_sched: add classful multiqueue dummy scheduler") > Signed-off-by: Zhengchao Shao <shaozhengchao@...wei.com> > --- > net/sched/sch_api.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c > index fdb8f429333d..dbc9cf5eea89 100644 > --- a/net/sched/sch_api.c > +++ b/net/sched/sch_api.c > @@ -1596,6 +1596,10 @@ static int tc_modify_qdisc(struct sk_buff *skb, struct nlmsghdr *n, > NL_SET_ERR_MSG(extack, "Qdisc parent/child loop detected"); > return -ELOOP; > } > + if (clid == TC_H_INGRESS) { > + NL_SET_ERR_MSG(extack, "Ingress cannot graft directly"); > + return -EINVAL; > + } > qdisc_refcount_inc(q); > goto graft; > } else { > -- > 2.34.1 > >
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