Re: BUG: unable to handle kernel paging request in fl_dump_key

[Cong Wang]

On Fri, May 15, 2020 at 6:53 AM syzbot
<syzbot+9c1be56e9317b795e874@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    99addbe3 net: broadcom: Select BROADCOM_PHY for BCMGENET
> git tree:       net
> console output: https://syzkaller.appspot.com/x/log.txt?x=173e568c100000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=b0212dbee046bc1f
> dashboard link: https://syzkaller.appspot.com/bug?extid=9c1be56e9317b795e874
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
>
> Unfortunately, I don't have any reproducer for this crash yet.
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+9c1be56e9317b795e874@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> BUG: unable to handle page fault for address: fffffbfff4a9538a
> #PF: supervisor read access in kernel mode
> #PF: error_code(0x0000) - not-present page
> PGD 21ffe5067 P4D 21ffe5067 PUD 21ffe4067 PMD 0
> Oops: 0000 [#1] PREEMPT SMP KASAN
> CPU: 1 PID: 5831 Comm: syz-executor.3 Not tainted 5.7.0-rc4-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:fl_dump_key+0x8c/0x1980 net/sched/cls_flower.c:2514
> Code: 04 f2 04 f2 c7 40 0c 04 f3 f3 f3 65 48 8b 04 25 28 00 00 00 48 89 84 24 b0 00 00 00 31 c0 e8 3b 0d 20 fb 48 89 e8 48 c1 e8 03 <42> 0f b6 04 30 84 c0 74 08 3c 03 0f 8e 6f 17 00 00 44 8b 75 00 31
> RSP: 0018:ffffc900019672d8 EFLAGS: 00010a03
> RAX: 1ffffffff4a9538a RBX: ffffffffa54a9a8f RCX: ffffc9000f733000
> RDX: 000000000000080f RSI: ffffffff86532275 RDI: ffff88808f68b800
> RBP: ffffffffa54a9c57 R08: ffff888096266200 R09: ffff888097a5603c
> R10: ffff888097a56036 R11: ffffed1012f4ac06 R12: ffff88808f68b800
> R13: ffff88806780a100 R14: dffffc0000000000 R15: ffff88806780a100
> FS:  00007f0a86395700(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: fffffbfff4a9538a CR3: 0000000099de6000 CR4: 00000000001406e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  fl_tmplt_dump+0xcf/0x250 net/sched/cls_flower.c:2784
>  tc_chain_fill_node+0x48e/0x7c0 net/sched/cls_api.c:2707
>  tc_chain_notify+0x189/0x2e0 net/sched/cls_api.c:2733
>  tc_ctl_chain+0xb82/0x1080 net/sched/cls_api.c:2919

I guess the chain template name must be specified by user:

diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index 0a7ecc292bd3..bcacb7db70c6 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -2782,8 +2782,10 @@ static int tc_chain_tmplt_add(struct tcf_chain
*chain, struct net *net,
        void *tmplt_priv;

        /* If kind is not set, user did not specify template. */
-       if (!tca[TCA_KIND])
-               return 0;
+       if (!tca[TCA_KIND]) {
+               NL_SET_ERR_MSG(extack, "TC chain template name is not
specified");
+               return -EINVAL;
+       }

        if (tcf_proto_check_kind(tca[TCA_KIND], name)) {
                NL_SET_ERR_MSG(extack, "Specified TC chain template
name too long");