bisecting fixing commit since 2cc3c4b3c2e9c99e90aaf19cd801ff2c160f283c
building syzkaller on 424dd8e7b52828cad44ce653a5d4ac30670f5e2c
testing commit 2cc3c4b3c2e9c99e90aaf19cd801ff2c160f283c with gcc (GCC) 8.1.0
kernel signature: 3fe34e472c07ea46976d4bd59151baf09621f45892ec19b81a44782bcb34771d
run #0: crashed: BUG: unable to handle kernel NULL pointer dereference in netif_napi_del
run #1: crashed: BUG: unable to handle kernel NULL pointer dereference in netif_napi_del
run #2: crashed: BUG: unable to handle kernel NULL pointer dereference in netif_napi_del
run #3: crashed: BUG: unable to handle kernel NULL pointer dereference in netif_napi_del
run #4: crashed: BUG: unable to handle kernel NULL pointer dereference in netif_napi_del
run #5: crashed: BUG: unable to handle kernel paging request in napi_hash_del
run #6: crashed: BUG: unable to handle kernel NULL pointer dereference in netif_napi_del
run #7: crashed: BUG: unable to handle kernel NULL pointer dereference in netif_napi_del
run #8: crashed: BUG: unable to handle kernel NULL pointer dereference in netif_napi_del
run #9: crashed: BUG: unable to handle kernel NULL pointer dereference in netif_napi_del
testing current HEAD f804b3159482eedbb4250b1e9248c308fb63b805
testing commit f804b3159482eedbb4250b1e9248c308fb63b805 with gcc (GCC) 8.1.0
kernel signature: 66a20f5e9a49ba6860385050faa80e765cced45142c1a983f86deac02aac48f9
all runs: crashed: BUG: unable to handle kernel NULL pointer dereference in free_netdev
revisions tested: 2, total time: 17m55.001505217s (build: 11m0.49898269s, test: 6m14.001329806s)
the crash still happens on HEAD
commit msg: Merge tag 'linux-watchdog-5.10-rc1' of git://www.linux-watchdog.org/linux-watchdog
crash: BUG: unable to handle kernel NULL pointer dereference in free_netdev
BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 11c8ce067 P4D 11c8ce067 PUD 11cbc6067 PMD 0 
Oops: 0000 [#1] PREEMPT SMP
CPU: 1 PID: 9350 Comm: syz-executor.3 Not tainted 5.9.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:free_netdev+0xae/0x140 net/core/dev.c:10545
Code: ef e8 a6 d9 00 00 48 8b 45 58 48 8b 08 48 8d b8 a0 fe ff ff 49 39 c4 48 8d 99 a0 fe ff ff 74 27 e8 57 fe ff ff e8 42 c9 ff ff <48> 8b 93 60 01 00 00 48 8d 83 60 01 00 00 48 89 df 4c 39 e0 48 8d
RSP: 0018:ffffc90004b9fa98 EFLAGS: 00010282
RAX: 0000000000000000 RBX: fffffffffffffea0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff83f2ab7b RDI: 0000000000000286
RBP: ffff88811dfc4000 R08: 0000000000000001 R09: 0000000000000001
R10: 0000000000000001 R11: 0000000000000000 R12: ffff88811dfc4058
R13: dead000000000100 R14: ffffc90004b9fab8 R15: ffffc90004b9fbb0
FS:  00007f433ba73700(0000) GS:ffff88813bd00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000011ec8b000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 netdev_run_todo+0x2f5/0x340 net/core/dev.c:10259
 rtnl_unlock net/core/rtnetlink.c:112 [inline]
 rtnetlink_rcv_msg+0x17b/0x480 net/core/rtnetlink.c:5564
 netlink_rcv_skb+0x49/0xf0 net/netlink/af_netlink.c:2494
 netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
 netlink_unicast+0x19a/0x270 net/netlink/af_netlink.c:1330
 netlink_sendmsg+0x248/0x480 net/netlink/af_netlink.c:1919
 sock_sendmsg_nosec net/socket.c:651 [inline]
 sock_sendmsg+0x2b/0x40 net/socket.c:671
 ____sys_sendmsg+0x1ed/0x230 net/socket.c:2353
 ___sys_sendmsg+0x77/0xb0 net/socket.c:2407
 __sys_sendmsg+0x52/0xa0 net/socket.c:2440
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45d239
Code: 5d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 2b b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f433ba72c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 000000000002c0c0 RCX: 000000000045d239
RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000005
RBP: 000000000118d020 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118cfec
R13: 00007fffce06a86f R14: 00007f433ba739c0 R15: 000000000118cfec
Modules linked in:
CR2: 0000000000000000
---[ end trace 26d46d2e8ce896cc ]---
RIP: 0010:free_netdev+0xae/0x140 net/core/dev.c:10545
Code: ef e8 a6 d9 00 00 48 8b 45 58 48 8b 08 48 8d b8 a0 fe ff ff 49 39 c4 48 8d 99 a0 fe ff ff 74 27 e8 57 fe ff ff e8 42 c9 ff ff <48> 8b 93 60 01 00 00 48 8d 83 60 01 00 00 48 89 df 4c 39 e0 48 8d
RSP: 0018:ffffc90004b9fa98 EFLAGS: 00010282
RAX: 0000000000000000 RBX: fffffffffffffea0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff83f2ab7b RDI: 0000000000000286
RBP: ffff88811dfc4000 R08: 0000000000000001 R09: 0000000000000001
R10: 0000000000000001 R11: 0000000000000000 R12: ffff88811dfc4058
R13: dead000000000100 R14: ffffc90004b9fab8 R15: ffffc90004b9fbb0
FS:  00007f433ba73700(0000) GS:ffff88813bd00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8ba6ff2db8 CR3: 000000011ec8b000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400