BUG: unable to handle kernel paging request in drm_fb_helper_dirty_work

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    e42617b8 Linux 5.5-rc1
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=126dc282e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=3754e2c78c1adb82
dashboard link: https://syzkaller.appspot.com/bug?extid=8a2039467425e497e64a
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
userspace arch: i386

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+8a2039467425e497e64a@xxxxxxxxxxxxxxxxxxxxxxxxx

BUG: unable to handle page fault for address: fffff520015a7200
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 7ffcd067 P4D 7ffcd067 PUD 2cd1c067 PMD 76d10067 PTE 0
Oops: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 18 Comm: kworker/1:0 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS  
rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
Workqueue: events drm_fb_helper_dirty_work
RIP: 0010:memory_is_nonzero mm/kasan/generic.c:121 [inline]
RIP: 0010:memory_is_poisoned_n mm/kasan/generic.c:135 [inline]
RIP: 0010:memory_is_poisoned mm/kasan/generic.c:166 [inline]
RIP: 0010:check_memory_region_inline mm/kasan/generic.c:182 [inline]
RIP: 0010:check_memory_region+0x9c/0x1a0 mm/kasan/generic.c:192
Code: c9 4d 0f 49 c1 49 c1 f8 03 45 85 c0 0f 84 10 01 00 00 41 83 e8 01 4e  
8d 44 c0 08 eb 0d 48 83 c0 08 4c 39 c0 0f 84 a7 00 00 00 <48> 83 38 00 74  
ed 4c 8d 40 08 eb 09 48 83 c0 01 49 39 c0 74 53 80
RSP: 0018:ffffc900004cfc30 EFLAGS: 00010216
RAX: fffff520015a7200 RBX: fffff520015a7400 RCX: ffffffff83f94dec
RDX: 0000000000000001 RSI: 0000000000001000 RDI: ffffc9000ad39000
RBP: ffffc900004cfc48 R08: fffff520015a7400 R09: 0000000000000200
R10: fffff520015a73ff R11: ffffc9000ad39fff R12: fffff520015a7200
R13: ffffc9000ad39000 R14: ffffc9000a53a000 R15: ffffc9000a53a000
FS:  0000000000000000(0000) GS:ffff88802d100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: fffff520015a7200 CR3: 0000000052ea7000 CR4: 0000000000340ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Call Trace:
 memcpy+0x38/0x50 mm/kasan/common.c:126
 memcpy include/linux/string.h:380 [inline]
 drm_fb_helper_dirty_blit_real drivers/gpu/drm/drm_fb_helper.c:399 [inline]
 drm_fb_helper_dirty_work+0x44c/0x780 drivers/gpu/drm/drm_fb_helper.c:428
 process_one_work+0x9af/0x1740 kernel/workqueue.c:2264
 worker_thread+0x98/0xe40 kernel/workqueue.c:2410
 kthread+0x361/0x430 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Modules linked in:
CR2: fffff520015a7200
---[ end trace 1682650b38de1096 ]---
RIP: 0010:memory_is_nonzero mm/kasan/generic.c:121 [inline]
RIP: 0010:memory_is_poisoned_n mm/kasan/generic.c:135 [inline]
RIP: 0010:memory_is_poisoned mm/kasan/generic.c:166 [inline]
RIP: 0010:check_memory_region_inline mm/kasan/generic.c:182 [inline]
RIP: 0010:check_memory_region+0x9c/0x1a0 mm/kasan/generic.c:192
Code: c9 4d 0f 49 c1 49 c1 f8 03 45 85 c0 0f 84 10 01 00 00 41 83 e8 01 4e  
8d 44 c0 08 eb 0d 48 83 c0 08 4c 39 c0 0f 84 a7 00 00 00 <48> 83 38 00 74  
ed 4c 8d 40 08 eb 09 48 83 c0 01 49 39 c0 74 53 80
RSP: 0018:ffffc900004cfc30 EFLAGS: 00010216
RAX: fffff520015a7200 RBX: fffff520015a7400 RCX: ffffffff83f94dec
RDX: 0000000000000001 RSI: 0000000000001000 RDI: ffffc9000ad39000
RBP: ffffc900004cfc48 R08: fffff520015a7400 R09: 0000000000000200
R10: fffff520015a73ff R11: ffffc9000ad39fff R12: fffff520015a7200
R13: ffffc9000ad39000 R14: ffffc9000a53a000 R15: ffffc9000a53a000
FS:  0000000000000000(0000) GS:ffff88802d100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: fffff520015a7200 CR3: 0000000052ea7000 CR4: 0000000000340ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600


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