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Subjectgeneral protection fault in fbcon_switch
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Hello,

syzbot found the following crash on:

HEAD commit: e17994d1 usb: core: kcov: collect coverage from usb comple..
git tree: https://github.com/google/kasan.git usb-fuzzer
console output: https://syzkaller.appspot.com/x/log.txt?x=1328834be00000
kernel config: https://syzkaller.appspot.com/x/.config?x=5d64370c438bc60
dashboard link: https://syzkaller.appspot.com/bug?extid=732528bae351682f1f27
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+732528bae351682f1f27@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc000000006c: 0000 [#1] SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000360-0x0000000000000367]
CPU: 0 PID: 5 Comm: kworker/0:0 Not tainted 5.6.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: usb_hub_wq hub_event
RIP: 0010:fbcon_switch+0x28f/0x1740 drivers/video/fbdev/core/fbcon.c:2260
Code: 0f 85 96 14 00 00 48 8d 04 db 48 8b 1c c5 00 91 ff 89 48 b8 00 00 00 00 00 fc ff df 48 8d bb 60 03 00 00 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e de 11 00 00 44 8b b3 60 03 00
RSP: 0018:ffff8881da1dead8 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffc9000d9eb000
RDX: 000000000000006c RSI: ffffffff81fe5b44 RDI: 0000000000000360
RBP: ffff8881ab4f0000 R08: ffff8881da196200 R09: fffffbfff0fcc10e
R10: fffffbfff0fcc10d R11: ffffffff87e6086f R12: ffff8881d6616000
R13: ffff8881c6a4a000 R14: 00000000000000a3 R15: ffffffff85ff8520
FS: 0000000000000000(0000) GS:ffff8881db200000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f676c8e2740 CR3: 00000001cfd06000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
redraw_screen+0x2a8/0x770 drivers/tty/vt/vt.c:1008
vc_do_resize+0xfe7/0x1360 drivers/tty/vt/vt.c:1295
fbcon_init+0x1221/0x1ab0 drivers/video/fbdev/core/fbcon.c:1219
visual_init+0x305/0x5c0 drivers/tty/vt/vt.c:1062
do_bind_con_driver+0x536/0x890 drivers/tty/vt/vt.c:3542
do_take_over_console+0x453/0x5b0 drivers/tty/vt/vt.c:4122
do_fbcon_takeover+0x10b/0x210 drivers/video/fbdev/core/fbcon.c:588
fbcon_fb_registered+0x26b/0x340 drivers/video/fbdev/core/fbcon.c:3259
do_register_framebuffer drivers/video/fbdev/core/fbmem.c:1664 [inline]
register_framebuffer+0x56e/0x980 drivers/video/fbdev/core/fbmem.c:1832
dlfb_usb_probe.cold+0x1743/0x1ba3 drivers/video/fbdev/udlfb.c:1735
usb_probe_interface+0x310/0x800 drivers/usb/core/driver.c:374
really_probe+0x290/0xac0 drivers/base/dd.c:551
driver_probe_device+0x223/0x350 drivers/base/dd.c:724
__device_attach_driver+0x1d1/0x290 drivers/base/dd.c:831
bus_for_each_drv+0x162/0x1e0 drivers/base/bus.c:431
__device_attach+0x217/0x390 drivers/base/dd.c:897
bus_probe_device+0x1e4/0x290 drivers/base/bus.c:491
device_add+0x1459/0x1bf0 drivers/base/core.c:2500
usb_set_configuration+0xe47/0x17d0 drivers/usb/core/message.c:2023
usb_generic_driver_probe+0x9d/0xe0 drivers/usb/core/generic.c:241
usb_probe_device+0xd9/0x230 drivers/usb/core/driver.c:272
really_probe+0x290/0xac0 drivers/base/dd.c:551
driver_probe_device+0x223/0x350 drivers/base/dd.c:724
__device_attach_driver+0x1d1/0x290 drivers/base/dd.c:831
bus_for_each_drv+0x162/0x1e0 drivers/base/bus.c:431
__device_attach+0x217/0x390 drivers/base/dd.c:897
bus_probe_device+0x1e4/0x290 drivers/base/bus.c:491
device_add+0x1459/0x1bf0 drivers/base/core.c:2500
usb_new_device.cold+0x540/0xcd0 drivers/usb/core/hub.c:2548
hub_port_connect drivers/usb/core/hub.c:5195 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5335 [inline]
port_event drivers/usb/core/hub.c:5481 [inline]
hub_event+0x21cb/0x4300 drivers/usb/core/hub.c:5563
process_one_work+0x94b/0x1620 kernel/workqueue.c:2264
process_scheduled_works kernel/workqueue.c:2326 [inline]
worker_thread+0x7ab/0xe20 kernel/workqueue.c:2412
kthread+0x318/0x420 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Modules linked in:
---[ end trace bae4913bb3cd6c7d ]---
RIP: 0010:fbcon_switch+0x28f/0x1740 drivers/video/fbdev/core/fbcon.c:2260
Code: 0f 85 96 14 00 00 48 8d 04 db 48 8b 1c c5 00 91 ff 89 48 b8 00 00 00 00 00 fc ff df 48 8d bb 60 03 00 00 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e de 11 00 00 44 8b b3 60 03 00
RSP: 0018:ffff8881da1dead8 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffc9000d9eb000
RDX: 000000000000006c RSI: ffffffff81fe5b44 RDI: 0000000000000360
RBP: ffff8881ab4f0000 R08: ffff8881da196200 R09: fffffbfff0fcc10e
R10: fffffbfff0fcc10d R11: ffffffff87e6086f R12: ffff8881d6616000
R13: ffff8881c6a4a000 R14: 00000000000000a3 R15: ffffffff85ff8520
FS: 0000000000000000(0000) GS:ffff8881db200000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f676c8e2740 CR3: 0000000007021000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this bug report. See:
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