bisecting fixing commit since 811218eceeaa7618652e1b8d11caeff67ab42072 building syzkaller on 98682e5e2aefc9aad61354f4f3ac93be96002a2a testing commit 811218eceeaa7618652e1b8d11caeff67ab42072 with gcc (GCC) 8.4.1 20210217 kernel signature: 1b7398c7648c77de26b354441ae900d87a13443f9a85304cdd77e5ee2f7b3b36 all runs: crashed: general protection fault in fq_codel_enqueue testing current HEAD fcfbdfe9626edd5bf00c732e093eed249ecdbfa1 testing commit fcfbdfe9626edd5bf00c732e093eed249ecdbfa1 with gcc (GCC) 8.4.1 20210217 kernel signature: e5d6542ad38b6d9a1baee14d3577fbe1463df7dcad4735f162ddc979ed42e7aa all runs: crashed: general protection fault in fq_codel_enqueue revisions tested: 2, total time: 22m46.742723387s (build: 15m45.417921407s, test: 6m38.06990304s) the crash still happens on HEAD commit msg: Linux 4.19.197 crash: general protection fault in fq_codel_enqueue batman_adv: batadv0: Interface activated: batadv_slave_1 kasan: CONFIG_KASAN_INLINE enabled batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3e) already exists on: batadv_slave_1 kasan: GPF could be caused by NULL-ptr deref or user memory access batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems! general protection fault: 0000 [#1] PREEMPT SMP KASAN CPU: 0 PID: 9826 Comm: syz-executor.5 Not tainted 4.19.197-syzkaller #0 batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3e) already exists on: batadv_slave_1 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:dequeue_head net/sched/sch_fq_codel.c:126 [inline] RIP: 0010:fq_codel_drop net/sched/sch_fq_codel.c:174 [inline] RIP: 0010:fq_codel_enqueue+0x865/0x12e0 net/sched/sch_fq_codel.c:236 Code: 48 89 7c 24 48 eb 0b 44 39 7c 24 58 0f 86 bb 00 00 00 48 8b 7c 24 50 80 3f 00 0f 85 82 06 00 00 4c 8b 20 4c 89 e2 48 c1 ea 03 <80> 3c 0a 00 0f 85 64 05 00 00 49 8b 14 24 49 8d 7c 24 28 48 89 10 RSP: 0018:ffff88809a64f540 EFLAGS: 00010246 RAX: ffff88808db608c0 RBX: ffff88809cd80040 RCX: dffffc0000000000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffed1011b6c118 RBP: ffff88809a64f630 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: ffff88809cd80328 R12: 0000000000000000 R13: 1ffff110134c9eb4 R14: ffff88809a64f780 R15: 0000000000000000 FS: 00007f59eb826700(0000) GS:ffff8880ba200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f9c1f0b4c20 CR3: 000000009c8da000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems! DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __dev_xmit_skb net/core/dev.c:3494 [inline] __dev_queue_xmit+0x1098/0x2900 net/core/dev.c:3807 batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3e) already exists on: batadv_slave_1 batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems! dev_queue_xmit+0xb/0x10 net/core/dev.c:3871 batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3e) already exists on: batadv_slave_1 __bpf_tx_skb net/core/filter.c:2015 [inline] __bpf_redirect_common net/core/filter.c:2054 [inline] __bpf_redirect+0x619/0xb60 net/core/filter.c:2061 ____bpf_clone_redirect net/core/filter.c:2094 [inline] bpf_clone_redirect+0x29b/0x3f0 net/core/filter.c:2066 bpf_prog_cc75667d52cf7bb0+0xe88/0x1000 batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems! IPv6: ADDRCONF(NETDEV_UP): batadv_slave_1: link is not ready bpf_test_run_one net/bpf/test_run.c:22 [inline] bpf_test_run+0xce/0x330 net/bpf/test_run.c:43 bpf_prog_test_run_skb+0x537/0xa90 net/bpf/test_run.c:147 batman_adv: batadv0: Interface activated: batadv_slave_1 bpf_prog_test_run kernel/bpf/syscall.c:1796 [inline] __do_sys_bpf kernel/bpf/syscall.c:2441 [inline] __se_sys_bpf+0x9af/0x2bf0 kernel/bpf/syscall.c:2384 __x64_sys_bpf+0x6e/0xb0 kernel/bpf/syscall.c:2384 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x465d99 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:00007f59eb826188 EFLAGS: 00000246 ORIG_RAX: 0000000000000141 RAX: ffffffffffffffda RBX: 000000000056c008 RCX: 0000000000465d99 RDX: 0000000000000048 RSI: 0000000020000140 RDI: 000000000000000a RBP: 00000000004bcf27 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056c008 R13: 00007ffe8120644f R14: 00007f59eb826300 R15: 0000000000022000 Modules linked in: ---[ end trace 7f823f87e401721b ]--- RIP: 0010:dequeue_head net/sched/sch_fq_codel.c:126 [inline] RIP: 0010:fq_codel_drop net/sched/sch_fq_codel.c:174 [inline] RIP: 0010:fq_codel_enqueue+0x865/0x12e0 net/sched/sch_fq_codel.c:236 Code: 48 89 7c 24 48 eb 0b 44 39 7c 24 58 0f 86 bb 00 00 00 48 8b 7c 24 50 80 3f 00 0f 85 82 06 00 00 4c 8b 20 4c 89 e2 48 c1 ea 03 <80> 3c 0a 00 0f 85 64 05 00 00 49 8b 14 24 49 8d 7c 24 28 48 89 10 RSP: 0018:ffff88809a64f540 EFLAGS: 00010246 RAX: ffff88808db608c0 RBX: ffff88809cd80040 RCX: dffffc0000000000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffed1011b6c118 RBP: ffff88809a64f630 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: ffff88809cd80328 R12: 0000000000000000 R13: 1ffff110134c9eb4 R14: ffff88809a64f780 R15: 0000000000000000 FS: 00007f59eb826700(0000) GS:ffff8880ba200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f9c1f0b4c20 CR3: 000000009c8da000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400