Re: BUG: unable to handle kernel paging request in sys_imageblit

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit:    435faf5c Merge tag 'riscv-for-linus-5.8-mw0' of git://git...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1768c725100000
kernel config:  https://syzkaller.appspot.com/x/.config?x=3dbb617b9c2a5bdf
dashboard link: https://syzkaller.appspot.com/bug?extid=33f89a9a6b6acd893b11
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
userspace arch: i386
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11f3f485100000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+33f89a9a6b6acd893b11@xxxxxxxxxxxxxxxxxxxxxxxxx

BUG: unable to handle page fault for address: fffff520013df608
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 7ffcd067 P4D 7ffcd067 PUD 2c920067 PMD 29858067 PTE 0
Oops: 0000 [#1] PREEMPT SMP KASAN
CPU: 2 PID: 8457 Comm: syz-executor.0 Not tainted 5.7.0-syzkaller #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
RIP: 0010:fast_imageblit drivers/video/fbdev/core/sysimgblt.c:229 [inline]
RIP: 0010:sys_imageblit+0x616/0x1240 drivers/video/fbdev/core/sysimgblt.c:275
Code: 0f b6 14 28 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 5c 0b 00 00 8b 44 24 20 4d 8d 77 04 4c 89 fa 48 c1 ea 03 23 07 <42> 0f b6 0c 2a 4c 89 fa 83 e2 07 33 44 24 14 83 c2 03 38 ca 7c 08
RSP: 0018:ffffc90001867578 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff888023ac8402 RCX: ffffffff88786a40
RDX: 1ffff920013df608 RSI: ffffffff83c3bbbc RDI: ffffffff88786a40
RBP: 0000000000000fef R08: ffff888029cf8040 R09: 0000000000000001
R10: ffffffff8a8b743f R11: fffffbfff1516e87 R12: 0000000000000007
R13: dffffc0000000000 R14: ffffc90009efb044 R15: ffffc90009efb040
FS:  0000000000000000(0000) GS:ffff88802d000000(0063) knlGS:00000000f7f0fb40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: fffff520013df608 CR3: 000000001b812000 CR4: 0000000000340ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 drm_fb_helper_sys_imageblit+0x1c/0x180 drivers/gpu/drm/drm_fb_helper.c:747
 bit_putcs_unaligned drivers/video/fbdev/core/bitblit.c:139 [inline]
 bit_putcs+0x8d0/0xd60 drivers/video/fbdev/core/bitblit.c:188
 fbcon_putcs+0x345/0x3f0 drivers/video/fbdev/core/fbcon.c:1362
 do_update_region+0x398/0x630 drivers/tty/vt/vt.c:683
 invert_screen+0x2a7/0x600 drivers/tty/vt/vt.c:800
 highlight drivers/tty/vt/selection.c:57 [inline]
 clear_selection drivers/tty/vt/selection.c:84 [inline]
 clear_selection+0x55/0x70 drivers/tty/vt/selection.c:80
 vc_do_resize+0xff3/0x1370 drivers/tty/vt/vt.c:1230
 fbcon_do_set_font+0x4a0/0x950 drivers/video/fbdev/core/fbcon.c:2608
 fbcon_set_font+0x732/0x870 drivers/video/fbdev/core/fbcon.c:2705
 con_font_set drivers/tty/vt/vt.c:4571 [inline]
 con_font_op+0xd65/0x1160 drivers/tty/vt/vt.c:4636
 compat_kdfontop_ioctl drivers/tty/vt/vt_ioctl.c:1151 [inline]
 vt_compat_ioctl+0x23a/0x6c0 drivers/tty/vt/vt_ioctl.c:1213
 tty_compat_ioctl+0x19c/0x410 drivers/tty/tty_io.c:2847
 __do_compat_sys_ioctl fs/ioctl.c:865 [inline]
 __se_compat_sys_ioctl fs/ioctl.c:816 [inline]
 __ia32_compat_sys_ioctl+0x23d/0x2b0 fs/ioctl.c:816
 do_syscall_32_irqs_on arch/x86/entry/common.c:337 [inline]
 do_fast_syscall_32+0x270/0xe90 arch/x86/entry/common.c:396
 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
Modules linked in:
CR2: fffff520013df608
---[ end trace fbceb2e52f6d552c ]---
RIP: 0010:fast_imageblit drivers/video/fbdev/core/sysimgblt.c:229 [inline]
RIP: 0010:sys_imageblit+0x616/0x1240 drivers/video/fbdev/core/sysimgblt.c:275
Code: 0f b6 14 28 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 5c 0b 00 00 8b 44 24 20 4d 8d 77 04 4c 89 fa 48 c1 ea 03 23 07 <42> 0f b6 0c 2a 4c 89 fa 83 e2 07 33 44 24 14 83 c2 03 38 ca 7c 08
RSP: 0018:ffffc90001867578 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff888023ac8402 RCX: ffffffff88786a40
RDX: 1ffff920013df608 RSI: ffffffff83c3bbbc RDI: ffffffff88786a40
RBP: 0000000000000fef R08: ffff888029cf8040 R09: 0000000000000001
R10: ffffffff8a8b743f R11: fffffbfff1516e87 R12: 0000000000000007
R13: dffffc0000000000 R14: ffffc90009efb044 R15: ffffc90009efb040
FS:  0000000000000000(0000) GS:ffff88802d000000(0063) knlGS:00000000f7f0fb40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: fffff520013df608 CR3: 000000001b812000 CR4: 0000000000340ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400