bisecting fixing commit since 2cc3c4b3c2e9c99e90aaf19cd801ff2c160f283c
building syzkaller on 424dd8e7b52828cad44ce653a5d4ac30670f5e2c
testing commit 2cc3c4b3c2e9c99e90aaf19cd801ff2c160f283c with gcc (GCC) 8.1.0
kernel signature: 9a1f494b95ccdd93265660918e49d83047bdfec444761f3261570ad1c885e189
all runs: crashed: BUG: unable to handle kernel NULL pointer dereference in netif_napi_del
testing current HEAD 9791581c049c10929e97098374dd1716a81fefcc
testing commit 9791581c049c10929e97098374dd1716a81fefcc with gcc (GCC) 8.1.0
kernel signature: 07019c3f8eac8fa5926175734cf6971402098cc65a7863d2ecd245526d4a6185
all runs: crashed: BUG: unable to handle kernel NULL pointer dereference in free_netdev
revisions tested: 2, total time: 16m27.049227523s (build: 9m40.647801155s, test: 6m3.761044573s)
the crash still happens on HEAD
commit msg: Merge tag 'for-5.11-rc4-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux
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 116461067 P4D 116461067 PUD 116ade067 PMD 0 
Oops: 0000 [#1] PREEMPT SMP
CPU: 0 PID: 7888 Comm: syz-executor.2 Not tainted 5.11.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:free_netdev+0xbb/0x190 net/core/dev.c:10658
Code: ef e8 49 dc 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 4a fe ff ff e8 b5 c8 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:ffffc900030a7a98 EFLAGS: 00010296
RAX: 0000000000000000 RBX: fffffffffffffea0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff83f4156b RDI: 0000000000000282
RBP: ffff888116a58000 R08: 0000000000000001 R09: 0000000000000001
R10: 0000000000000001 R11: 0000000000000000 R12: ffff888116a58058
R13: 0000000000000000 R14: ffffc900030a7ab8 R15: ffffc900030a7bb0
FS:  00007f7bc942a700(0000) GS:ffff888237c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000114453000 CR4: 0000000000350ef0
Call Trace:
 netdev_run_todo+0x2e1/0x330 net/core/dev.c:10346
 rtnl_unlock net/core/rtnetlink.c:112 [inline]
 rtnetlink_rcv_msg+0x17b/0x480 net/core/rtnetlink.c:5554
 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:652 [inline]
 sock_sendmsg+0x2b/0x40 net/socket.c:672
 ____sys_sendmsg+0x1ed/0x230 net/socket.c:2345
 ___sys_sendmsg+0x77/0xb0 net/socket.c:2399
 __sys_sendmsg+0x52/0xa0 net/socket.c:2432
 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:00007f7bc9429c78 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: 00007ffd81e2280f R14: 00007f7bc942a9c0 R15: 000000000118cfec
Modules linked in:
CR2: 0000000000000000
---[ end trace 4f56c30482037e3a ]---
RIP: 0010:free_netdev+0xbb/0x190 net/core/dev.c:10658
Code: ef e8 49 dc 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 4a fe ff ff e8 b5 c8 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:ffffc900030a7a98 EFLAGS: 00010296
RAX: 0000000000000000 RBX: fffffffffffffea0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff83f4156b RDI: 0000000000000282
RBP: ffff888116a58000 R08: 0000000000000001 R09: 0000000000000001
R10: 0000000000000001 R11: 0000000000000000 R12: ffff888116a58058
R13: 0000000000000000 R14: ffffc900030a7ab8 R15: ffffc900030a7bb0
FS:  00007f7bc942a700(0000) GS:ffff888237c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000114453000 CR4: 0000000000350ef0