BUG: unable to handle kernel NULL pointer dereference in cfg80211_wext_siwrts

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    2f806c2a Merge branch 'net-ungraft-prio'
git tree:       net
console output: https://syzkaller.appspot.com/x/log.txt?x=1032069ee00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5c90cac8f1f8c619
dashboard link: https://syzkaller.appspot.com/bug?extid=34b582cf32c1db008f8e
compiler:       gcc (GCC) 9.0.0 20181231 (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+34b582cf32c1db008f8e@xxxxxxxxxxxxxxxxxxxxxxxxx

BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor instruction fetch in kernel mode
#PF: error_code(0x0010) - not-present page
PGD a7499067 P4D a7499067 PUD 9a778067 PMD 0
Oops: 0010 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 12180 Comm: syz-executor.2 Not tainted 5.5.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:0x0
Code: Bad RIP value.
RSP: 0018:ffffc90001727a78 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: ffff888218678540 RCX: ffffc9000e5df000
RDX: 1ffffffff1148744 RSI: 0000000000000008 RDI: ffff888218678540
RBP: ffffc90001727ab8 R08: ffff8880957ac0c0 R09: ffffed1015d2703d
R10: ffffed1015d2703c R11: ffff8880ae9381e3 R12: ffffffff88a438a0
R13: ffff88808f309000 R14: ffffc90001727bb0 R15: 0000000000000000
FS:  00007f1e9f870700(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 0000000094518000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 rdev_set_wiphy_params net/wireless/rdev-ops.h:542 [inline]
 cfg80211_wext_siwrts+0x265/0x8f0 net/wireless/wext-compat.c:267
 ioctl_standard_call+0xca/0x1d0 net/wireless/wext-core.c:1015
 wireless_process_ioctl.constprop.0+0x236/0x2b0 net/wireless/wext-core.c:953
 wext_ioctl_dispatch net/wireless/wext-core.c:986 [inline]
 wext_ioctl_dispatch net/wireless/wext-core.c:974 [inline]
 wext_handle_ioctl+0x106/0x1c0 net/wireless/wext-core.c:1047
 sock_ioctl+0x47d/0x790 net/socket.c:1112
 vfs_ioctl fs/ioctl.c:47 [inline]
 file_ioctl fs/ioctl.c:545 [inline]
 do_vfs_ioctl+0x977/0x14e0 fs/ioctl.c:732
 ksys_ioctl+0xab/0xd0 fs/ioctl.c:749
 __do_sys_ioctl fs/ioctl.c:756 [inline]
 __se_sys_ioctl fs/ioctl.c:754 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:754
 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45af49
Code: ad b6 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 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f1e9f86fc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045af49
RDX: 0000000020000040 RSI: 0000000000008b22 RDI: 0000000000000004
RBP: 000000000075c070 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f1e9f8706d4
R13: 00000000004c2837 R14: 00000000004d8b30 R15: 00000000ffffffff
Modules linked in:
CR2: 0000000000000000
---[ end trace 4579299d7d6f7d47 ]---
RIP: 0010:0x0
Code: Bad RIP value.
RSP: 0018:ffffc90001727a78 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: ffff888218678540 RCX: ffffc9000e5df000
RDX: 1ffffffff1148744 RSI: 0000000000000008 RDI: ffff888218678540
RBP: ffffc90001727ab8 R08: ffff8880957ac0c0 R09: ffffed1015d2703d
R10: ffffed1015d2703c R11: ffff8880ae9381e3 R12: ffffffff88a438a0
R13: ffff88808f309000 R14: ffffc90001727bb0 R15: 0000000000000000
FS:  00007f1e9f870700(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fff5d5b8fc8 CR3: 0000000094518000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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