Messages in this thread Patch in this message | | | Subject | Re: [syzbot] BUG: unable to handle kernel NULL pointer dereference in htb_select_queue | From | Maxim Mikityanskiy <> | Date | Wed, 10 Mar 2021 16:54:24 +0200 |
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On 2021-03-09 17:20, Eric Dumazet wrote: > > > On 3/9/21 4:13 PM, syzbot wrote: >> Hello, >> >> syzbot found the following issue on: >> >> HEAD commit: 38b5133a octeontx2-pf: Fix otx2_get_fecparam() >> git tree: net-next >> console output: https://syzkaller.appspot.com/x/log.txt?x=166288a8d00000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=dbc1ca9e55dc1f9f >> dashboard link: https://syzkaller.appspot.com/bug?extid=b53a709f04722ca12a3c >> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=119454ccd00000 >> >> The issue was bisected to: >> >> commit d03b195b5aa015f6c11988b86a3625f8d5dbac52 >> Author: Maxim Mikityanskiy <maximmi@mellanox.com> >> Date: Tue Jan 19 12:08:13 2021 +0000 >> >> sch_htb: Hierarchical QoS hardware offload >> >> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=13ab12ecd00000 >> final oops: https://syzkaller.appspot.com/x/report.txt?x=106b12ecd00000 >> console output: https://syzkaller.appspot.com/x/log.txt?x=17ab12ecd00000 >> >> IMPORTANT: if you fix the issue, please add the following tag to the commit: >> Reported-by: syzbot+b53a709f04722ca12a3c@syzkaller.appspotmail.com >> Fixes: d03b195b5aa0 ("sch_htb: Hierarchical QoS hardware offload") >> >> BUG: kernel NULL pointer dereference, address: 0000000000000000 >> #PF: supervisor instruction fetch in kernel mode >> #PF: error_code(0x0010) - not-present page >> PGD 183fe067 P4D 183fe067 PUD 21aef067 PMD 0 >> Oops: 0010 [#1] PREEMPT SMP KASAN >> CPU: 0 PID: 10125 Comm: syz-executor.0 Not tainted 5.11.0-rc7-syzkaller #0 >> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 >> RIP: 0010:0x0 >> Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6. >> RSP: 0018:ffffc9000a9c74e8 EFLAGS: 00010246 >> RAX: dffffc0000000000 RBX: 1ffff92001538e9e RCX: 0000000000000000 >> RDX: ffffc9000a9c7520 RSI: 0000000000000012 RDI: ffff88802d158000 >> RBP: ffff88802d158000 R08: 00000000fffffff1 R09: 0000000000000400 >> R10: ffffffff871631c4 R11: 0000000000000000 R12: ffffffff89ea6b40 >> R13: dffffc0000000000 R14: ffff888012b79c00 R15: 00000000ffff0000 >> FS: 00007f73f9698700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000 >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> CR2: ffffffffffffffd6 CR3: 00000000173b5000 CR4: 00000000001506f0 >> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 >> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 >> Call Trace: >> htb_offload net/sched/sch_htb.c:1011 [inline] >> htb_select_queue+0x17f/0x2c0 net/sched/sch_htb.c:1349 >> tc_modify_qdisc+0x44a/0x1a50 net/sched/sch_api.c:1657 >> rtnetlink_rcv_msg+0x44e/0xad0 net/core/rtnetlink.c:5553 >> netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2502 >> netlink_unicast_kernel net/netlink/af_netlink.c:1312 [inline] >> netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1338 >> netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1927 >> sock_sendmsg_nosec net/socket.c:652 [inline] >> sock_sendmsg+0xcf/0x120 net/socket.c:672 >> ____sys_sendmsg+0x6e8/0x810 net/socket.c:2348 >> ___sys_sendmsg+0xf3/0x170 net/socket.c:2402 >> __sys_sendmsg+0xe5/0x1b0 net/socket.c:2435 >> do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 >> entry_SYSCALL_64_after_hwframe+0x44/0xa9 >> RIP: 0033:0x466019 >> Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48 >> RSP: 002b:00007f73f9698188 EFLAGS: 00000246 ORIG_RAX: 000000000000002e >> RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 0000000000466019 >> RDX: 0000000000000000 RSI: 00000000200007c0 RDI: 0000000000000004 >> RBP: 00000000004bd067 R08: 0000000000000000 R09: 0000000000000000 >> R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60 >> R13: 00007fffefccc11f R14: 00007f73f9698300 R15: 0000000000022000 >> Modules linked in: >> CR2: 0000000000000000 >> ---[ end trace e1544e8206616773 ]--- >> RIP: 0010:0x0 >> Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6. >> RSP: 0018:ffffc9000a9c74e8 EFLAGS: 00010246 >> RAX: dffffc0000000000 RBX: 1ffff92001538e9e RCX: 0000000000000000 >> RDX: ffffc9000a9c7520 RSI: 0000000000000012 RDI: ffff88802d158000 >> RBP: ffff88802d158000 R08: 00000000fffffff1 R09: 0000000000000400 >> R10: ffffffff871631c4 R11: 0000000000000000 R12: ffffffff89ea6b40 >> R13: dffffc0000000000 R14: ffff888012b79c00 R15: 00000000ffff0000 >> FS: 00007f73f9698700(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000 >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> CR2: ffffffffffffffd6 CR3: 00000000173b5000 CR4: 00000000001506e0 >> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 >> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 >> >> >> --- >> This report is generated by a bot. It may contain errors. >> See https://goo.gl/tpsmEJ for more information about syzbot. >> syzbot engineers can be reached at syzkaller@googlegroups.com. >> >> syzbot will keep track of this issue. See: >> https://goo.gl/tpsmEJ#status for how to communicate with syzbot. >> For information about bisection process see: https://goo.gl/tpsmEJ#bisection >> syzbot can test patches for this issue, for details see: >> https://goo.gl/tpsmEJ#testing-patches >> > > > Hmm... what about this : > > diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c > index f87d07736a1404edcfd17a792321758cd4bdd173..680afb5bfe2294a5531c7aaeed698b95ea3ab20c 100644 > --- a/net/sched/sch_api.c > +++ b/net/sched/sch_api.c > @@ -1651,15 +1651,16 @@ static int tc_modify_qdisc(struct sk_buff *skb, struct nlmsghdr *n, > err = -ENOENT; > } > } else { > - struct netdev_queue *dev_queue; > + struct netdev_queue *dev_queue = NULL; > > if (p && p->ops->cl_ops && p->ops->cl_ops->select_queue) > dev_queue = p->ops->cl_ops->select_queue(p, tcm); > - else if (p) > - dev_queue = p->dev_queue; > - else > - dev_queue = netdev_get_tx_queue(dev, 0); > - > + if (!dev_queue) { > + if (p) > + dev_queue = p->dev_queue; > + else > + dev_queue = netdev_get_tx_queue(dev, 0); > + } > q = qdisc_create(dev, dev_queue, p, > tcm->tcm_parent, tcm->tcm_handle, > tca, &err, extack); > diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c > index dff3adf5a9156c2412c64a10ad1b2ce9e1367433..cc6eccd688701ae00255f07e32fb4b0efbaf45ce 100644 > --- a/net/sched/sch_htb.c > +++ b/net/sched/sch_htb.c > @@ -1008,6 +1008,8 @@ static void htb_set_lockdep_class_child(struct Qdisc *q) > > static int htb_offload(struct net_device *dev, struct tc_htb_qopt_offload *opt) > { > + if (!tc_can_offload(dev) || !dev->netdev_ops->ndo_setup_tc) > + return -EOPNOTSUPP;
My fault, all calls to htb_offload must be protected by if (q->offload). Rather than checking tc_can_offload and ndo_setup_tc in htb_offload every time, I suggest to fix htb_select_queue:
diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c index dff3adf5a915..b23203159996 100644 --- a/net/sched/sch_htb.c +++ b/net/sched/sch_htb.c @@ -1340,8 +1340,12 @@ htb_select_queue(struct Qdisc *sch, struct tcmsg *tcm) { struct net_device *dev = qdisc_dev(sch); struct tc_htb_qopt_offload offload_opt; + struct htb_sched *q = qdisc_priv(sch); int err;
+ if (!q->offload) + return sch->dev_queue; + offload_opt = (struct tc_htb_qopt_offload) { .command = TC_HTB_LEAF_QUERY_QUEUE, .classid = TC_H_MIN(tcm->tcm_parent), htb_init ensures that tc_can_offload and ndo_setup_tc are checked if q->offload is true. Also, we can avoid changing tc_modify_qdisc if htb_select_queue mimics its behavior in non-offload mode, as shown above.
There is also a case where htb_select_queue returns NULL on errors, and that is handled in qdisc_create (the error message will be "No device queue given"), which I think is a sane behavior.
What do you think of this fix? If it fits, I'll send it as a patch.
> return dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_HTB, opt); > } > >
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