Re: [syzbot] general protection fault in fq_codel_enqueue (3)

[Eric Dumazet]

On 10/29/21 8:55 AM, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    1fc596a56b33 Merge tag 'trace-v5.15-rc6' of git://git.kern..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1453dc04b00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=b160d0631c7a8f26
> dashboard link: https://syzkaller.appspot.com/bug?extid=7a12909485b94426aceb
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=154a0b64b00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=177eec86b00000
> 
> Bisection is inconclusive: the issue happens on the oldest tested release.
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=154fc86ab00000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=174fc86ab00000
> console output: https://syzkaller.appspot.com/x/log.txt?x=134fc86ab00000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+7a12909485b94426aceb@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
> KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
> CPU: 1 PID: 6542 Comm: syz-executor965 Not tainted 5.15.0-rc7-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:dequeue_head net/sched/sch_fq_codel.c:120 [inline]
> RIP: 0010:fq_codel_drop net/sched/sch_fq_codel.c:168 [inline]
> RIP: 0010:fq_codel_enqueue+0x83e/0x10c0 net/sched/sch_fq_codel.c:230
> Code: f8 e2 25 fa 45 39 ec 0f 83 cb 00 00 00 e8 1a dc 25 fa 48 8b 44 24 10 80 38 00 0f 85 9a 06 00 00 49 8b 07 48 89 c2 48 c1 ea 03 <42> 80 3c 32 00 0f 85 6e 06 00 00 48 8b 10 48 8d 78 28 49 89 17 48
> RSP: 0018:ffffc90001187310 EFLAGS: 00010246
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: ffffffff87504776 RDI: 0000000000000003
> RBP: ffffc900011874e0 R08: 0000000000000400 R09: 0000000000000001
> R10: ffffffff875046d6 R11: 0000000000000000 R12: 0000000000000400
> R13: 0000000000000000 R14: dffffc0000000000 R15: ffff888071660000
> FS:  0000555556b21300(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f9c09885040 CR3: 0000000021c77000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  dev_qdisc_enqueue+0x40/0x300 net/core/dev.c:3771
>  __dev_xmit_skb net/core/dev.c:3855 [inline]
>  __dev_queue_xmit+0x1f0e/0x36e0 net/core/dev.c:4170
>  __bpf_tx_skb net/core/filter.c:2114 [inline]
>  __bpf_redirect_no_mac net/core/filter.c:2139 [inline]
>  __bpf_redirect+0x5ba/0xd20 net/core/filter.c:2162
>  ____bpf_clone_redirect net/core/filter.c:2429 [inline]
>  bpf_clone_redirect+0x2ae/0x420 net/core/filter.c:2401
>  ___bpf_prog_run+0x3592/0x77d0 kernel/bpf/core.c:1548
>  __bpf_prog_run512+0x91/0xd0 kernel/bpf/core.c:1776
>  bpf_dispatcher_nop_func include/linux/bpf.h:718 [inline]
>  __bpf_prog_run include/linux/filter.h:624 [inline]
>  bpf_prog_run include/linux/filter.h:631 [inline]
>  bpf_test_run+0x37c/0xa20 net/bpf/test_run.c:119
>  bpf_prog_test_run_skb+0xa7c/0x1cb0 net/bpf/test_run.c:662
>  bpf_prog_test_run kernel/bpf/syscall.c:3307 [inline]
>  __sys_bpf+0x2137/0x5df0 kernel/bpf/syscall.c:4605
>  __do_sys_bpf kernel/bpf/syscall.c:4691 [inline]
>  __se_sys_bpf kernel/bpf/syscall.c:4689 [inline]
>  __x64_sys_bpf+0x75/0xb0 kernel/bpf/syscall.c:4689
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x7fef7c1e24d9
> Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 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 c0 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffc95c98158 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fef7c1e24d9
> RDX: 0000000000000048 RSI: 0000000020000140 RDI: 000000000000000a
> RBP: 00007fef7c1a64c0 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007fef7c1a6550
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> Modules linked in:
> ---[ end trace 0597f54336b28fa4 ]---
> RIP: 0010:dequeue_head net/sched/sch_fq_codel.c:120 [inline]
> RIP: 0010:fq_codel_drop net/sched/sch_fq_codel.c:168 [inline]
> RIP: 0010:fq_codel_enqueue+0x83e/0x10c0 net/sched/sch_fq_codel.c:230
> Code: f8 e2 25 fa 45 39 ec 0f 83 cb 00 00 00 e8 1a dc 25 fa 48 8b 44 24 10 80 38 00 0f 85 9a 06 00 00 49 8b 07 48 89 c2 48 c1 ea 03 <42> 80 3c 32 00 0f 85 6e 06 00 00 48 8b 10 48 8d 78 28 49 89 17 48
> RSP: 0018:ffffc90001187310 EFLAGS: 00010246
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: ffffffff87504776 RDI: 0000000000000003
> RBP: ffffc900011874e0 R08: 0000000000000400 R09: 0000000000000001
> R10: ffffffff875046d6 R11: 0000000000000000 R12: 0000000000000400
> R13: 0000000000000000 R14: dffffc0000000000 R15: ffff888071660000
> FS:  0000555556b21300(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f9c09885040 CR3: 0000000021c77000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> ----------------
> Code disassembly (best guess):
>    0:	f8                   	clc
>    1:	e2 25                	loop   0x28
>    3:	fa                   	cli
>    4:	45 39 ec             	cmp    %r13d,%r12d
>    7:	0f 83 cb 00 00 00    	jae    0xd8
>    d:	e8 1a dc 25 fa       	callq  0xfa25dc2c
>   12:	48 8b 44 24 10       	mov    0x10(%rsp),%rax
>   17:	80 38 00             	cmpb   $0x0,(%rax)
>   1a:	0f 85 9a 06 00 00    	jne    0x6ba
>   20:	49 8b 07             	mov    (%r15),%rax
>   23:	48 89 c2             	mov    %rax,%rdx
>   26:	48 c1 ea 03          	shr    $0x3,%rdx
> * 2a:	42 80 3c 32 00       	cmpb   $0x0,(%rdx,%r14,1) <-- trapping instruction
>   2f:	0f 85 6e 06 00 00    	jne    0x6a3
>   35:	48 8b 10             	mov    (%rax),%rdx
>   38:	48 8d 78 28          	lea    0x28(%rax),%rdi
>   3c:	49 89 17             	mov    %rdx,(%r15)
>   3f:	48                   	rex.W
> 
> 
> ---
> 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@xxxxxxxxxxxxxxxx.
> 
> 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
> 

This is the bug I mentioned in https://marc.info/?l=linux-netdev&m=163552087226957&w=2