BUG: unable to handle kernel paging request in vga16fb_fillrect (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f96eb53cbd76 Linux 4.14.246
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=13b072a5300000
kernel config: https://syzkaller.appspot.com/x/.config?x=678b722a9f6422ef
dashboard link: https://syzkaller.appspot.com/bug?extid=89b280d944b001a50ae4
compiler: gcc version 10.2.1 20210110 (Debian 10.2.1-6)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=126beaa5300000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=129767b1300000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+89b280...@syzkaller.appspotmail.com

BUG: unable to handle kernel paging request at ffff888001000050
IP: writeb arch/x86/include/asm/io.h:65 [inline]
IP: vga16fb_fillrect+0x910/0x1820 drivers/video/fbdev/vga16fb.c:923
PGD c9cf067 P4D c9cf067 PUD c9d0067 PMD 80000000010001e1
Oops: 0003 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 0 PID: 7989 Comm: syz-executor270 Not tainted 4.14.246-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff888097172500 task.stack: ffff8880a32b0000
RIP: 0010:writeb arch/x86/include/asm/io.h:65 [inline]
RIP: 0010:vga16fb_fillrect+0x910/0x1820 drivers/video/fbdev/vga16fb.c:923
RSP: 0018:ffff8880a32b73e0 EFLAGS: 00010297
RAX: ffff888097172500 RBX: ffff888001000050 RCX: 00000000000000c0
RDX: 0000000000000000 RSI: ffff8880a32b7470 RDI: ffff8880a32b7480
RBP: 000000000000001b R08: 0000000000000001 R09: ffffed1047111893
R10: ffff88823888c49f R11: 0000000000000000 R12: 000000000ffeb800
R13: 00000000000000a5 R14: ffff88800100006b R15: 0000000000000000
FS: 00000000009cd300(0000) GS:ffff8880ba400000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff888001000050 CR3: 00000000b3e3a000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
bit_clear_margins+0x3af/0x480 drivers/video/fbdev/core/bitblit.c:224
fbcon_clear_margins+0x1bb/0x300 drivers/video/fbdev/core/fbcon.c:1266
fbcon_switch+0xde0/0x19e0 drivers/video/fbdev/core/fbcon.c:2133
redraw_screen+0x32c/0x790 drivers/tty/vt/vt.c:689
fbcon_modechanged+0x673/0x8d0 drivers/video/fbdev/core/fbcon.c:2665
fbcon_event_notify+0x107/0x1760 drivers/video/fbdev/core/fbcon.c:3016
notifier_call_chain+0x108/0x1a0 kernel/notifier.c:93
__blocking_notifier_call_chain kernel/notifier.c:317 [inline]
__blocking_notifier_call_chain kernel/notifier.c:304 [inline]
blocking_notifier_call_chain kernel/notifier.c:328 [inline]
blocking_notifier_call_chain+0x79/0x90 kernel/notifier.c:325
fb_set_var+0xb3b/0xd20 drivers/video/fbdev/core/fbmem.c:1058
do_fb_ioctl+0x36d/0xa70 drivers/video/fbdev/core/fbmem.c:1131
fb_ioctl+0xdd/0x130 drivers/video/fbdev/core/fbmem.c:1246
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:500 [inline]
do_vfs_ioctl+0x75a/0xff0 fs/ioctl.c:684
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x7f/0xb0 fs/ioctl.c:692
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x43efd9
RSP: 002b:00007ffced794e88 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000400488 RCX: 000000000043efd9
RDX: 0000000020000200 RSI: 0000000000004601 RDI: 0000000000000003
RBP: 0000000000402fc0 R08: 0000000000000000 R09: 0000000000400488
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000403050
R13: 0000000000000000 R14: 00000000004ac018 R15: 0000000000400488
Code: 85 e4 0f 84 ea fc ff ff e8 4e 3c 18 fe 4d 63 ed 45 31 ff e8 43 3c 18 fe 41 89 ee 49 01 de 85 ed 0f 84 7c 06 00 00 e8 30 3c 18 fe <44> 88 3b 48 83 c3 01 4c 39 f3 75 ef e8 1f 3c 18 fe 4b 8d 1c 2e
RIP: writeb arch/x86/include/asm/io.h:65 [inline] RSP: ffff8880a32b73e0
RIP: vga16fb_fillrect+0x910/0x1820 drivers/video/fbdev/vga16fb.c:923 RSP: ffff8880a32b73e0
CR2: ffff888001000050
---[ end trace 8c89f355b31faba4 ]---
----------------
Code disassembly (best guess):
0: 85 e4 test %esp,%esp
2: 0f 84 ea fc ff ff je 0xfffffcf2
8: e8 4e 3c 18 fe callq 0xfe183c5b
d: 4d 63 ed movslq %r13d,%r13
10: 45 31 ff xor %r15d,%r15d
13: e8 43 3c 18 fe callq 0xfe183c5b
18: 41 89 ee mov %ebp,%r14d
1b: 49 01 de add %rbx,%r14
1e: 85 ed test %ebp,%ebp
20: 0f 84 7c 06 00 00 je 0x6a2
26: e8 30 3c 18 fe callq 0xfe183c5b
* 2b: 44 88 3b mov %r15b,(%rbx) <-- trapping instruction
2e: 48 83 c3 01 add $0x1,%rbx
32: 4c 39 f3 cmp %r14,%rbx
35: 75 ef jne 0x26
37: e8 1f 3c 18 fe callq 0xfe183c5b
3c: 4b 8d 1c 2e lea (%r14,%r13,1),%rbx


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