bisecting fixing commit since dce0f88600e49746b4bda873965b671a23ff4313 building syzkaller on f90ec89960664f503e0811d8b67c56bb1128d47d testing commit dce0f88600e49746b4bda873965b671a23ff4313 compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: 35e944c53438fd9758ffa4e29dec459784414994a9cca3b897b066e626013388 all runs: crashed: general protection fault in vxlan_fdb_destroy testing current HEAD b172b44fcb1771e083aad806fa96f3f60e2ddfac testing commit b172b44fcb1771e083aad806fa96f3f60e2ddfac compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: 5fb53316e5268108c29655c14a6ed7e5420f955d3f978d6b0f937da393f221a0 all runs: crashed: general protection fault in vxlan_fdb_destroy revisions tested: 2, total time: 26m25.600340024s (build: 19m16.682812556s, test: 6m25.999541873s) the crash still happens on HEAD commit msg: Linux 4.19.206 crash: general protection fault in vxlan_fdb_destroy IPv6: ADDRCONF(NETDEV_CHANGE): batadv_slave_1: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_batadv: link becomes ready netlink: 24 bytes leftover after parsing attributes in process `syz-executor.2'. 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: 1 PID: 7210 Comm: syz-executor.2 Not tainted 4.19.206-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:__hlist_del include/linux/list.h:679 [inline] RIP: 0010:hlist_del_rcu include/linux/rculist.h:457 [inline] RIP: 0010:vxlan_fdb_destroy+0x9e/0x180 drivers/net/vxlan.c:788 Code: 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 d8 00 00 00 48 b8 00 00 00 00 00 fc ff df 4c 8b 6b 08 4c 89 ea 48 c1 ea 03 <80> 3c 02 00 0f 85 ac 00 00 00 4d 85 e4 4d 89 65 00 74 25 49 8d 7c RSP: 0018:ffff8881cf6bed10 EFLAGS: 00010a02 RAX: dffffc0000000000 RBX: ffff8881e8dab780 RCX: 1ffff1103af849bf RDX: 1bd5a00000000040 RSI: ffff8881e8dab780 RDI: ffff8881e8dab788 RBP: ffff8881cf6bed30 R08: ffff8881d8444f50 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: dead000000000200 R14: ffff8881cf6bee00 R15: 00000000fffffff0 FS: 00007f51d8cb4700(0000) GS:ffff8881f6900000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000000051c630 CR3: 00000001d9f0a006 CR4: 00000000001606e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __vxlan_dev_create+0x3bb/0x750 drivers/net/vxlan.c:3279 vxlan_newlink+0xa1/0xe0 drivers/net/vxlan.c:3506 rtnl_newlink+0xce2/0x1360 net/core/rtnetlink.c:3141 rtnetlink_rcv_msg+0x34f/0x950 net/core/rtnetlink.c:4782 netlink_rcv_skb+0x13e/0x3d0 net/netlink/af_netlink.c:2457 rtnetlink_rcv+0x10/0x20 net/core/rtnetlink.c:4800 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline] netlink_unicast+0x443/0x660 net/netlink/af_netlink.c:1346 netlink_sendmsg+0x667/0xc60 net/netlink/af_netlink.c:1911 sock_sendmsg_nosec net/socket.c:651 [inline] sock_sendmsg+0xac/0xf0 net/socket.c:661 kernel_sendmsg+0x26/0x30 net/socket.c:681 sock_no_sendpage+0xfd/0x140 net/core/sock.c:2668 kernel_sendpage+0x60/0xd0 net/socket.c:3585 sock_sendpage+0x6d/0xd0 net/socket.c:912 pipe_to_sendpage+0x212/0x430 fs/splice.c:452 splice_from_pipe_feed fs/splice.c:503 [inline] __splice_from_pipe+0x2cb/0x720 fs/splice.c:627 splice_from_pipe+0xbb/0x120 fs/splice.c:662 generic_splice_sendpage+0x10/0x20 fs/splice.c:833 do_splice_from fs/splice.c:852 [inline] do_splice fs/splice.c:1154 [inline] __do_sys_splice fs/splice.c:1428 [inline] __se_sys_splice+0x71e/0x17e0 fs/splice.c:1408 __x64_sys_splice+0xdc/0x1a0 fs/splice.c:1408 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4645a9 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:00007f51d8cb4198 EFLAGS: 00000246 ORIG_RAX: 0000000000000113 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000004645a9 RDX: 0000000000000006 RSI: 0000000000000000 RDI: 0000000000000004 RBP: 0000000000523120 R08: 000000000004ffe2 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000055bfa0 R13: 00007f51d8cb46bc R14: 00000000ffffffff R15: 0000000000000006 Modules linked in: ---[ end trace af7c6acb542ececb ]--- RIP: 0010:__write_once_size include/linux/compiler.h:288 [inline] RIP: 0010:__hlist_del include/linux/list.h:679 [inline] RIP: 0010:hlist_del_rcu include/linux/rculist.h:457 [inline] RIP: 0010:vxlan_fdb_destroy+0x9e/0x180 drivers/net/vxlan.c:788 Code: 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 d8 00 00 00 48 b8 00 00 00 00 00 fc ff df 4c 8b 6b 08 4c 89 ea 48 c1 ea 03 <80> 3c 02 00 0f 85 ac 00 00 00 4d 85 e4 4d 89 65 00 74 25 49 8d 7c RSP: 0018:ffff8881cf6bed10 EFLAGS: 00010a02 RAX: dffffc0000000000 RBX: ffff8881e8dab780 RCX: 1ffff1103af849bf RDX: 1bd5a00000000040 RSI: ffff8881e8dab780 RDI: ffff8881e8dab788 RBP: ffff8881cf6bed30 R08: ffff8881d8444f50 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: dead000000000200 R14: ffff8881cf6bee00 R15: 00000000fffffff0 FS: 00007f51d8cb4700(0000) GS:ffff8881f6900000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000000055c000 CR3: 00000001d9f0a006 CR4: 00000000001606e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 ---------------- Code disassembly (best guess), 3 bytes skipped: 0: df 48 89 fisttps -0x77(%rax) 3: fa cli 4: 48 c1 ea 03 shr $0x3,%rdx 8: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) c: 0f 85 d8 00 00 00 jne 0xea 12: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax 19: fc ff df 1c: 4c 8b 6b 08 mov 0x8(%rbx),%r13 20: 4c 89 ea mov %r13,%rdx 23: 48 c1 ea 03 shr $0x3,%rdx * 27: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction 2b: 0f 85 ac 00 00 00 jne 0xdd 31: 4d 85 e4 test %r12,%r12 34: 4d 89 65 00 mov %r12,0x0(%r13) 38: 74 25 je 0x5f 3a: 49 rex.WB 3b: 8d .byte 0x8d 3c: 7c .byte 0x7c