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Subject[syzbot] general protection fault in fq_codel_enqueue (3)
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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@syzkaller.appspotmail.com

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@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

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