KASAN: stack-out-of-bounds Write in sys_imageblit

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4fa640dc Merge tag 'vfio-v5.8-rc7' of git://github.com/awi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17ec2d58900000
kernel config: https://syzkaller.appspot.com/x/.config?x=575b381064b1cba2
dashboard link: https://syzkaller.appspot.com/bug?extid=ba5bd977df7bb87862c4
compiler: gcc (GCC) 10.1.0-syz 20200507
userspace arch: i386

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ba5bd9...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: stack-out-of-bounds in fast_imageblit drivers/video/fbdev/core/sysimgblt.c:229 [inline]
BUG: KASAN: stack-out-of-bounds in sys_imageblit+0x117f/0x1290 drivers/video/fbdev/core/sysimgblt.c:275
Write of size 4 at addr ffffc900097d7d90 by task syz-executor.1/11925

CPU: 1 PID: 11925 Comm: syz-executor.1 Not tainted 5.8.0-rc6-syzkaller #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x18f/0x20d lib/dump_stack.c:118
print_address_description.constprop.0.cold+0x5/0x436 mm/kasan/report.c:383
__kasan_report mm/kasan/report.c:513 [inline]
kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
fast_imageblit drivers/video/fbdev/core/sysimgblt.c:229 [inline]
sys_imageblit+0x117f/0x1290 drivers/video/fbdev/core/sysimgblt.c:275
drm_fb_helper_sys_imageblit+0x1c/0x180 drivers/gpu/drm/drm_fb_helper.c:763
bit_putcs_unaligned drivers/video/fbdev/core/bitblit.c:139 [inline]
bit_putcs+0x6e1/0xd20 drivers/video/fbdev/core/bitblit.c:188
fbcon_putcs+0x33c/0x3f0 drivers/video/fbdev/core/fbcon.c:1362
do_update_region+0x399/0x630 drivers/tty/vt/vt.c:683
invert_screen+0x1d4/0x600 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+0x1099/0x13f0 drivers/tty/vt/vt.c:1230
fbcon_do_set_font+0x4ad/0x950 drivers/video/fbdev/core/fbcon.c:2609
fbcon_set_font+0x767/0x8b0 drivers/video/fbdev/core/fbcon.c:2706
con_font_set drivers/tty/vt/vt.c:4571 [inline]
con_font_op+0xd25/0x1110 drivers/tty/vt/vt.c:4636
vt_ioctl+0x1180/0x2670 drivers/tty/vt/vt_ioctl.c:928
vt_compat_ioctl+0x168/0x6b0 drivers/tty/vt/vt_ioctl.c:1249
tty_compat_ioctl+0x19c/0x410 drivers/tty/tty_io.c:2847
__do_compat_sys_ioctl+0x1d3/0x230 fs/ioctl.c:847
do_syscall_32_irqs_on+0x3f/0x60 arch/x86/entry/common.c:428
__do_fast_syscall_32 arch/x86/entry/common.c:475 [inline]
do_fast_syscall_32+0x7f/0x120 arch/x86/entry/common.c:503
entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
RIP: 0023:0xf7f48569
Code: Bad RIP value.
RSP: 002b:00000000f5d430bc EFLAGS: 00000296 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000004b61
RDX: 0000000020000080 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000


Memory state around the buggy address:
ffffc900097d7c80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffffc900097d7d00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffc900097d7d80: 00 00 f1 f1 f1 f1 00 00 f3 f3 00 00 00 00 00 00
^
ffffc900097d7e00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffffc900097d7e80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.