Hello,

syzbot found the following crash on:

HEAD commit: 596cf45c Merge branch 'akpm' (patches from Andrew) git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=17be842ee00000 kernel config: https://syzkaller.appspot.com/x/.config?x=7d8ab2e0e09c2a82 dashboard link: https://syzkaller.appspot.com/bug?extid=69fbd3e01470f169c8c4 compiler: gcc (GCC) 9.0.0 20181231 (experimental) syz repro: https://syzkaller.appspot.com/x/repro.syz?x=159c2861e00000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16b5d59ce00000

Bisection is inconclusive: the bug happens on the oldest tested release.

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=161f2cdee00000 console output: https://syzkaller.appspot.com/x/log.txt?x=111f2cdee00000

IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+69fbd3e01470f169c8c4@syzkaller.appspotmail.com

================================================================== BUG: KASAN: global-out-of-bounds in vga_8planes_imageblit drivers/video/fbdev/vga16fb.c:1140 [inline] BUG: KASAN: global-out-of-bounds in vga_imageblit_expand drivers/video/fbdev/vga16fb.c:1203 [inline] BUG: KASAN: global-out-of-bounds in vga16fb_imageblit+0x1c8b/0x2200 drivers/video/fbdev/vga16fb.c:1260 Read of size 2 at addr ffffffff8874be58 by task syz-executor421/8988

CPU: 0 PID: 8988 Comm: syz-executor421 Not tainted 5.4.0-syzkaller #0 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+0x197/0x210 lib/dump_stack.c:118 print_address_description.constprop.0.cold+0x5/0x30b mm/kasan/report.c:374 __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506 kasan_report+0x12/0x20 mm/kasan/common.c:638 __asan_report_load2_noabort+0x14/0x20 mm/kasan/generic_report.c:133 vga_8planes_imageblit drivers/video/fbdev/vga16fb.c:1140 [inline] vga_imageblit_expand drivers/video/fbdev/vga16fb.c:1203 [inline] vga16fb_imageblit+0x1c8b/0x2200 drivers/video/fbdev/vga16fb.c:1260 soft_cursor+0x4fb/0xa30 drivers/video/fbdev/core/softcursor.c:74 bit_cursor+0x12fc/0x1a60 drivers/video/fbdev/core/bitblit.c:386 fbcon_cursor+0x487/0x660 drivers/video/fbdev/core/fbcon.c:1402 hide_cursor+0x9d/0x2b0 drivers/tty/vt/vt.c:895 redraw_screen+0x60b/0x7d0 drivers/tty/vt/vt.c:988 vc_do_resize+0x10c9/0x1460 drivers/tty/vt/vt.c:1284 vc_resize+0x4d/0x60 drivers/tty/vt/vt.c:1304 fbcon_modechanged+0x367/0x790 drivers/video/fbdev/core/fbcon.c:2980 fbcon_update_vcs+0x42/0x50 drivers/video/fbdev/core/fbcon.c:3038 fb_set_var+0xb32/0xdd0 drivers/video/fbdev/core/fbmem.c:1051 do_fb_ioctl+0x390/0x7d0 drivers/video/fbdev/core/fbmem.c:1104 fb_ioctl+0xe6/0x130 drivers/video/fbdev/core/fbmem.c:1180 vfs_ioctl fs/ioctl.c:47 [inline] file_ioctl fs/ioctl.c:539 [inline] do_vfs_ioctl+0xdb6/0x13e0 fs/ioctl.c:726 ksys_ioctl+0xab/0xd0 fs/ioctl.c:743 __do_sys_ioctl fs/ioctl.c:750 [inline] __se_sys_ioctl fs/ioctl.c:748 [inline] __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:748 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x440309 Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007ffe5b970878 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440309 RDX: 0000000020000100 RSI: 0000000000004601 RDI: 0000000000000003 RBP: 00000000006ca018 R08: 0000000000000000 R09: 00000000004002c8 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401b90 R13: 0000000000401c20 R14: 0000000000000000 R15: 0000000000000000

The buggy address belongs to the variable: transl_h+0x38/0x40

Memory state around the buggy address: ffffffff8874bd00: 00 00 00 00 fa fa fa fa 00 00 00 00 fa fa fa fa ffffffff8874bd80: 00 00 00 00 00 fa fa fa fa fa fa fa 04 fa fa fa

ffffffff8874be00: fa fa fa fa 00 00 00 00 fa fa fa fa 00 00 00 00

^ ffffffff8874be80: fa fa fa fa 00 01 fa fa fa fa fa fa 00 00 00 04 ffffffff8874bf00: fa fa fa fa 00 00 04 fa fa fa fa fa 00 00 00 00 ==================================================================

--- This bug is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this bug report. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. For information about bisection process see: https://goo.gl/tpsmEJ#bisection syzbot can test patches for this bug, for details see: https://goo.gl/tpsmEJ#testing-patches