KASAN: global-out-of-bounds Read in tpg_print_str_4

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 85758777c2a2 Merge tag 'hwmon-for-v4.20-rc2' of git://git...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=157af45d400000
kernel config: https://syzkaller.appspot.com/x/.config?x=8f559fee2fc3375a
dashboard link: https://syzkaller.appspot.com/bug?extid=ccf0a61ed12f2a7313ee
compiler: gcc (GCC) 8.0.1 20180413 (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+ccf0a6...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: global-out-of-bounds in tpg_print_str_4+0xbc9/0xd70
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:1820
Read of size 1 at addr ffffffff88631c50 by task vivid-000-vid-c/7282

CPU: 0 PID: 7282 Comm: vivid-000-vid-c Not tainted 4.20.0-rc1+ #228
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x244/0x39d lib/dump_stack.c:113
print_address_description.cold.7+0x58/0x1ff mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412
__asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430
tpg_print_str_4+0xbc9/0xd70
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:1820
tpg_gen_text+0x4ba/0x540 drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:1874
vivid_fillbuff+0x3ff7/0x68e0
drivers/media/platform/vivid/vivid-kthread-cap.c:532
vivid_thread_vid_cap_tick
drivers/media/platform/vivid/vivid-kthread-cap.c:709 [inline]
vivid_thread_vid_cap+0xbc1/0x2650
drivers/media/platform/vivid/vivid-kthread-cap.c:813
kthread+0x35a/0x440 kernel/kthread.c:246
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

The buggy address belongs to the variable:
font_vga_8x16+0x50/0x60

Memory state around the buggy address:
ffffffff88631b00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffffffff88631b80: 00 00 00 00 fa fa fa fa 00 fa fa fa fa fa fa fa
> ffffffff88631c00: 00 00 00 00 00 fa fa fa fa fa fa fa 00 00 00 00
^
ffffffff88631c80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffffffff88631d00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


---
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[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit: ccda4af0f4b9 Linux 4.20-rc2
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1779cb0b400000
kernel config: https://syzkaller.appspot.com/x/.config?x=4a0a89f12ca9b0f5

dashboard link: https://syzkaller.appspot.com/bug?extid=ccf0a61ed12f2a7313ee
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
userspace arch: i386

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=126f0ed5400000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15ed6c25400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+ccf0a6...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: global-out-of-bounds in tpg_print_str_4+0xbc9/0xd70
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:1820

Read of size 1 at addr ffffffff88632850 by task vivid-000-vid-c/5989

CPU: 0 PID: 5989 Comm: vivid-000-vid-c Not tainted 4.20.0-rc2+ #236

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x244/0x39d lib/dump_stack.c:113
print_address_description.cold.7+0x58/0x1ff mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412
__asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430
tpg_print_str_4+0xbc9/0xd70
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:1820
tpg_gen_text+0x4ba/0x540 drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:1874
vivid_fillbuff+0x3ff7/0x68e0
drivers/media/platform/vivid/vivid-kthread-cap.c:532
vivid_thread_vid_cap_tick
drivers/media/platform/vivid/vivid-kthread-cap.c:709 [inline]
vivid_thread_vid_cap+0xbc1/0x2650
drivers/media/platform/vivid/vivid-kthread-cap.c:813
kthread+0x35a/0x440 kernel/kthread.c:246
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

The buggy address belongs to the variable:
font_vga_8x16+0x50/0x60

Memory state around the buggy address:

ffffffff88632700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffffffff88632780: 00 00 00 00 fa fa fa fa 00 fa fa fa fa fa fa fa
> ffffffff88632800: 00 00 00 00 00 fa fa fa fa fa fa fa 00 00 00 00
^
ffffffff88632880: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffffffff88632900: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================