bisecting fixing commit since c63ee2939dc1c6eee6c544af1b4ab441490bfe6e building syzkaller on 598ca6c8b8766304c3b2865e38f5f301c39bd299 testing commit c63ee2939dc1c6eee6c544af1b4ab441490bfe6e compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: c19dc70bfa9584291a865d4c144492c8ce9ea105067432b4ad55002d0757426b run #0: crashed: general protection fault in skb_unlink run #1: crashed: general protection fault in skb_unlink run #2: crashed: general protection fault in skb_unlink run #3: crashed: general protection fault in skb_unlink run #4: crashed: general protection fault in skb_unlink run #5: crashed: general protection fault in skb_unlink run #6: crashed: general protection fault in skb_unlink run #7: crashed: general protection fault in skb_unlink run #8: crashed: general protection fault in skb_unlink run #9: crashed: general protection fault in skb_unlink run #10: crashed: general protection fault in skb_unlink run #11: crashed: general protection fault in skb_unlink run #12: crashed: general protection fault in skb_unlink run #13: crashed: general protection fault in skb_unlink run #14: crashed: general protection fault in skb_unlink run #15: crashed: general protection fault in skb_unlink run #16: crashed: general protection fault in skb_unlink run #17: crashed: general protection fault in requeue_rx_msgs run #18: crashed: general protection fault in skb_unlink run #19: crashed: general protection fault in skb_unlink testing current HEAD 59456c9cc40c8f75b5a7efa0fe1f211d9c6fcaf1 testing commit 59456c9cc40c8f75b5a7efa0fe1f211d9c6fcaf1 compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: 02dea8e0af62e89f5d0ebde404f3a4ddb59b0f946373e06e8e4a7a259935d462 run #0: crashed: general protection fault in skb_unlink run #1: crashed: general protection fault in skb_unlink run #2: crashed: general protection fault in skb_unlink run #3: crashed: general protection fault in skb_unlink run #4: crashed: general protection fault in skb_unlink run #5: crashed: general protection fault in skb_unlink run #6: crashed: general protection fault in skb_unlink run #7: crashed: general protection fault in skb_unlink run #8: crashed: general protection fault in requeue_rx_msgs run #9: crashed: general protection fault in skb_unlink revisions tested: 2, total time: 27m23.675153205s (build: 20m11.705423975s, test: 6m19.208985891s) the crash still happens on HEAD commit msg: Linux 4.19.204 crash: general protection fault in skb_unlink IPv6: ADDRCONF(NETDEV_CHANGE): vxcan1: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): vxcan0: link becomes ready 8021q: adding VLAN 0 to HW filter on device batadv0 kasan: CONFIG_KASAN_INLINE enabled kasan: GPF could be caused by NULL-ptr deref or user memory access general protection fault: 0000 [#1] PREEMPT SMP KASAN CPU: 0 PID: 6682 Comm: syz-executor.2 Not tainted 4.19.204-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:__write_once_size include/linux/compiler.h:288 [inline] RIP: 0010:__skb_unlink include/linux/skbuff.h:1919 [inline] RIP: 0010:skb_unlink+0xe7/0x1a0 net/core/skbuff.c:2963 Code: 00 00 49 8d 7d 08 4c 8b 63 08 48 ba 00 00 00 00 00 fc ff df 48 c7 43 08 00 00 00 00 48 89 f9 48 c7 03 00 00 00 00 48 c1 e9 03 <80> 3c 11 00 75 63 4c 89 e1 4d 89 65 08 48 ba 00 00 00 00 00 fc ff RSP: 0018:ffff8881e02c7838 EFLAGS: 00010002 RAX: 0000000000000286 RBX: ffff8881dee32c00 RCX: 0000000000000001 RDX: dffffc0000000000 RSI: 000000000000001f RDI: 0000000000000008 RBP: ffff8881e02c7868 R08: ffffed103be96c35 R09: ffffed103be96c34 R10: ffffed103be96c34 R11: ffff8881df4b61a3 R12: 0000000000000000 R13: 0000000000000000 R14: 000000000000001e R15: ffff8881df4b61a0 FS: 00007f8bae13e700(0000) GS:ffff8881f6800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000004be8a0 CR3: 00000001df17a003 CR4: 00000000001606f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: kcm_recvmsg+0x3a5/0x5a0 net/kcm/kcmsock.c:1160 sock_recvmsg_nosec+0x7b/0xd0 net/socket.c:859 ___sys_recvmsg+0x219/0x500 net/socket.c:2387 __sys_recvmmsg+0x21d/0x650 net/socket.c:2499 do_sys_recvmmsg net/socket.c:2575 [inline] do_sys_recvmmsg+0x111/0x130 net/socket.c:2564 __do_sys_recvmmsg net/socket.c:2593 [inline] __se_sys_recvmmsg net/socket.c:2589 [inline] __x64_sys_recvmmsg+0xb9/0x150 net/socket.c:2589 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x461fc9 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:00007f8bae13e1a8 EFLAGS: 00000246 ORIG_RAX: 000000000000012b RAX: ffffffffffffffda RBX: 000000000052bf00 RCX: 0000000000461fc9 RDX: 0400000000000310 RSI: 0000000020003540 RDI: 0000000000000005 RBP: 0000000000000005 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 00000000004f7980 R14: 00000000004b412d R15: 00007f8bae13e6bc Modules linked in: ---[ end trace 7fda03b01c66199c ]--- RIP: 0010:__write_once_size include/linux/compiler.h:288 [inline] RIP: 0010:__skb_unlink include/linux/skbuff.h:1919 [inline] RIP: 0010:skb_unlink+0xe7/0x1a0 net/core/skbuff.c:2963 Code: 00 00 49 8d 7d 08 4c 8b 63 08 48 ba 00 00 00 00 00 fc ff df 48 c7 43 08 00 00 00 00 48 89 f9 48 c7 03 00 00 00 00 48 c1 e9 03 <80> 3c 11 00 75 63 4c 89 e1 4d 89 65 08 48 ba 00 00 00 00 00 fc ff RSP: 0018:ffff8881e02c7838 EFLAGS: 00010002 RAX: 0000000000000286 RBX: ffff8881dee32c00 RCX: 0000000000000001 RDX: dffffc0000000000 RSI: 000000000000001f RDI: 0000000000000008 RBP: ffff8881e02c7868 R08: ffffed103be96c35 R09: ffffed103be96c34 R10: ffffed103be96c34 R11: ffff8881df4b61a3 R12: 0000000000000000 R13: 0000000000000000 R14: 000000000000001e R15: ffff8881df4b61a0 FS: 00007f8bae13e700(0000) GS:ffff8881f6800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000004be8a0 CR3: 00000001df17a003 CR4: 00000000001606f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 ---------------- Code disassembly (best guess): 0: 00 00 add %al,(%rax) 2: 49 8d 7d 08 lea 0x8(%r13),%rdi 6: 4c 8b 63 08 mov 0x8(%rbx),%r12 a: 48 ba 00 00 00 00 00 movabs $0xdffffc0000000000,%rdx 11: fc ff df 14: 48 c7 43 08 00 00 00 movq $0x0,0x8(%rbx) 1b: 00 1c: 48 89 f9 mov %rdi,%rcx 1f: 48 c7 03 00 00 00 00 movq $0x0,(%rbx) 26: 48 c1 e9 03 shr $0x3,%rcx * 2a: 80 3c 11 00 cmpb $0x0,(%rcx,%rdx,1) <-- trapping instruction 2e: 75 63 jne 0x93 30: 4c 89 e1 mov %r12,%rcx 33: 4d 89 65 08 mov %r12,0x8(%r13) 37: 48 rex.W 38: ba 00 00 00 00 mov $0x0,%edx 3d: 00 fc add %bh,%ah 3f: ff .byte 0xff