[syzbot] [fbdev?] general protection fault in soft_cursor

[syzbot <syzbot+d910bd780e6efac35869@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    eb0f1697d729 Merge branch 'for-next/core', remote-tracking..
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=10e08bde280000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8860074b9a9d6c45
dashboard link: https://syzkaller.appspot.com/bug?extid=d910bd780e6efac35869
compiler:       Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2
userspace arch: arm64
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=103d17a9280000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1151bb19280000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/034232da7cff/disk-eb0f1697.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b11411bec33e/vmlinux-eb0f1697.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a53c52e170dd/Image-eb0f1697.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d910bd780e6efac35869@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: null-ptr-deref in soft_cursor+0x384/0x6b4 drivers/video/fbdev/core/softcursor.c:70
Read of size 16 at addr 0000000000000200 by task kworker/u4:1/12

CPU: 0 PID: 12 Comm: kworker/u4:1 Not tainted 6.4.0-rc3-syzkaller-geb0f1697d729 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/28/2023
Workqueue: events_power_efficient fb_flashcursor
Call trace:
 dump_backtrace+0x1b8/0x1e4 arch/arm64/kernel/stacktrace.c:233
 show_stack+0x2c/0x44 arch/arm64/kernel/stacktrace.c:240
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xd0/0x124 lib/dump_stack.c:106
 print_report+0xe4/0x514 mm/kasan/report.c:465
 kasan_report+0xd4/0x130 mm/kasan/report.c:572
 kasan_check_range+0x264/0x2a4 mm/kasan/generic.c:187
 __asan_memcpy+0x3c/0x84 mm/kasan/shadow.c:105
 soft_cursor+0x384/0x6b4 drivers/video/fbdev/core/softcursor.c:70
 bit_cursor+0x113c/0x1a64 drivers/video/fbdev/core/bitblit.c:377
 fb_flashcursor+0x35c/0x54c drivers/video/fbdev/core/fbcon.c:380
 process_one_work+0x788/0x12d4 kernel/workqueue.c:2405
 worker_thread+0x8e0/0xfe8 kernel/workqueue.c:2552
 kthread+0x288/0x310 kernel/kthread.c:379
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:853
==================================================================


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