BUG: unable to handle kernel NULL pointer dereference in do_select

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    90368a37fbbe Merge tag 'printk-for-4.18-rc3' of git://git...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1759737f800000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a63be0c83e84d370
dashboard link: https://syzkaller.appspot.com/bug?extid=cdb0d3176b53d35ad454
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+cdb0d3176b53d35ad454@xxxxxxxxxxxxxxxxxxxxxxxxx

netlink: 8 bytes leftover after parsing attributes in process  
`syz-executor4'.
kvm [7726]: vcpu0, guest rIP: 0x9166 disabled perfctr wrmsr: 0xc1 data 0xb8
BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
PGD 1b10e9067 P4D 1b10e9067 PUD 1b3a1f067 PMD 0
Oops: 0010 [#1] SMP KASAN
CPU: 0 PID: 7772 Comm: syz-executor5 Not tainted 4.18.0-rc2+ #121
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:          (null)
Code: Bad RIP value.
RSP: 0018:ffff88019746f438 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8801d270f140 RCX: ffffc90005628000
RDX: ffff88019746f6f0 RSI: ffff8801d270f140 RDI: ffff8801b273d800
RBP: ffff88019746f4e0 R08: ffff880195b58640 R09: ffffed003b5c46d6
R10: 0000000000000003 R11: 0000000000000000 R12: ffff88019746f6f0
R13: ffff8801b273d800 R14: ffffffff8818a920 R15: ffff880195c6e980
FS:  00007f300e4bb700(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 00000001a8e4d000 CR4: 00000000001426f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 vfs_poll include/linux/poll.h:86 [inline]
 do_select+0xac4/0x1b00 fs/select.c:507
 core_sys_select+0x78a/0xb80 fs/select.c:650
 do_pselect+0x241/0x4e0 fs/select.c:731
 __do_sys_pselect6 fs/select.c:772 [inline]
 __se_sys_pselect6 fs/select.c:757 [inline]
 __x64_sys_pselect6+0x1f7/0x280 fs/select.c:757
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x455a99
Code: 1d ba 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 eb b9 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f300e4bac68 EFLAGS: 00000246 ORIG_RAX: 000000000000010e
RAX: ffffffffffffffda RBX: 00007f300e4bb6d4 RCX: 0000000000455a99
RDX: 0000000020768000 RSI: 0000000020f33fc0 RDI: 0000000000000040
RBP: 000000000072bea0 R08: 0000000020349000 R09: 0000000020f14000
R10: 0000000020086000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004c0708 R14: 00000000004d0140 R15: 0000000000000000
Modules linked in:
Dumping ftrace buffer:
   (ftrace buffer empty)
CR2: 0000000000000000
---[ end trace f41162cfde74d2ca ]---
RIP: 0010:          (null)
Code: Bad RIP value.
RSP: 0018:ffff88019746f438 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8801d270f140 RCX: ffffc90005628000
RDX: ffff88019746f6f0 RSI: ffff8801d270f140 RDI: ffff8801b273d800
RBP: ffff88019746f4e0 R08: ffff880195b58640 R09: ffffed003b5c46d6
R10: 0000000000000003 R11: 0000000000000000 R12: ffff88019746f6f0
R13: ffff8801b273d800 R14: ffffffff8818a920 R15: ffff880195c6e980
FS:  00007f300e4bb700(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 00000001a8e4d000 CR4: 00000000001426f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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