Re: [syzbot] KASAN: vmalloc-out-of-bounds Write in imageblit (2)

From: syzbot
Date: Thu Jan 20 2022 - 17:58:32 EST

syzbot has found a reproducer for the following issue on:

HEAD commit: 7fc5253f5a13 Add linux-next specific files for 20220120
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=16385270700000
kernel config: https://syzkaller.appspot.com/x/.config?x=94e8da4df9ab6319
dashboard link: https://syzkaller.appspot.com/bug?extid=14b0e8f3fd1612e35350
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=155dde3db00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=125298e0700000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+14b0e8f3fd1612e35350@xxxxxxxxxxxxxxxxxxxxxxxxx

BUG: unable to handle page fault for address: fffff520008b2208
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 23ffed067 P4D 23ffed067 PUD 10db4067 PMD 1470c4067 PTE 0
Oops: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 3595 Comm: syz-executor362 Not tainted 5.16.0-next-20220120-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:fast_imageblit drivers/video/fbdev/core/sysimgblt.c:229 [inline]
RIP: 0010:sys_imageblit+0x656/0x1430 drivers/video/fbdev/core/sysimgblt.c:275
Code: 14 38 48 89 d8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 b6 0c 00 00 8b 44 24 20 23 03 8b 5c 24 18 31 c3 48 89 e8 48 c1 e8 03 <42> 0f b6 14 38 48 89 e8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85
RSP: 0018:ffffc90002a1f368 EFLAGS: 00010a02
RAX: 1ffff920008b2208 RBX: 0000000000000000 RCX: 0000000000000007
RDX: 0000000000000000 RSI: ffffffff84257bf0 RDI: 0000000000000003
RBP: ffffc90004591040 R08: 000000000000001f R09: ffffffff84257a74
R10: ffffffff84257be1 R11: 0000000000000020 R12: 0000000000000007
R13: 00000000000003ef R14: ffff888146efc7e0 R15: dffffc0000000000
FS: 0000555555c5d300(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: fffff520008b2208 CR3: 0000000023b12000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
drm_fb_helper_sys_imageblit drivers/gpu/drm/drm_fb_helper.c:794 [inline]
drm_fbdev_fb_imageblit+0x15c/0x350 drivers/gpu/drm/drm_fb_helper.c:2288
bit_putcs_unaligned drivers/video/fbdev/core/bitblit.c:124 [inline]
bit_putcs+0x6e1/0xd20 drivers/video/fbdev/core/bitblit.c:173
fbcon_putcs+0x353/0x440 drivers/video/fbdev/core/fbcon.c:1277
do_update_region+0x399/0x630 drivers/tty/vt/vt.c:676
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+0xe6e/0x1180 drivers/tty/vt/vt.c:1257
fbcon_do_set_font+0x47a/0x760 drivers/video/fbdev/core/fbcon.c:1928
fbcon_set_font+0x817/0xa00 drivers/video/fbdev/core/fbcon.c:2014
con_font_set drivers/tty/vt/vt.c:4666 [inline]
con_font_op+0x73a/0xc90 drivers/tty/vt/vt.c:4710
vt_k_ioctl drivers/tty/vt/vt_ioctl.c:474 [inline]
vt_ioctl+0x1e26/0x2b10 drivers/tty/vt/vt_ioctl.c:752
tty_ioctl+0xbbd/0x1660 drivers/tty/tty_io.c:2778
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl fs/ioctl.c:860 [inline]
__x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f3bac0e1349
Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 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 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffff160a718 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f3bac0e1349
RDX: 0000000020000000 RSI: 0000000000004b72 RDI: 0000000000000004
RBP: 00007f3bac0a51d0 R08: 000000000000000d R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f3bac0a5260
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>
Modules linked in:
CR2: fffff520008b2208
---[ end trace 0000000000000000 ]---
RIP: 0010:fast_imageblit drivers/video/fbdev/core/sysimgblt.c:229 [inline]
RIP: 0010:sys_imageblit+0x656/0x1430 drivers/video/fbdev/core/sysimgblt.c:275
Code: 14 38 48 89 d8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 b6 0c 00 00 8b 44 24 20 23 03 8b 5c 24 18 31 c3 48 89 e8 48 c1 e8 03 <42> 0f b6 14 38 48 89 e8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85
RSP: 0018:ffffc90002a1f368 EFLAGS: 00010a02
RAX: 1ffff920008b2208 RBX: 0000000000000000 RCX: 0000000000000007
RDX: 0000000000000000 RSI: ffffffff84257bf0 RDI: 0000000000000003
RBP: ffffc90004591040 R08: 000000000000001f R09: ffffffff84257a74
R10: ffffffff84257be1 R11: 0000000000000020 R12: 0000000000000007
R13: 00000000000003ef R14: ffff888146efc7e0 R15: dffffc0000000000
FS: 0000555555c5d300(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: fffff520008b2208 CR3: 0000000023b12000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 14 38 adc $0x38,%al
2: 48 89 d8 mov %rbx,%rax
5: 83 e0 07 and $0x7,%eax
8: 83 c0 03 add $0x3,%eax
b: 38 d0 cmp %dl,%al
d: 7c 08 jl 0x17
f: 84 d2 test %dl,%dl
11: 0f 85 b6 0c 00 00 jne 0xccd
17: 8b 44 24 20 mov 0x20(%rsp),%eax
1b: 23 03 and (%rbx),%eax
1d: 8b 5c 24 18 mov 0x18(%rsp),%ebx
21: 31 c3 xor %eax,%ebx
23: 48 89 e8 mov %rbp,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 42 0f b6 14 38 movzbl (%rax,%r15,1),%edx <-- trapping instruction
2f: 48 89 e8 mov %rbp,%rax
32: 83 e0 07 and $0x7,%eax
35: 83 c0 03 add $0x3,%eax
38: 38 d0 cmp %dl,%al
3a: 7c 08 jl 0x44
3c: 84 d2 test %dl,%dl
3e: 0f .byte 0xf
3f: 85 .byte 0x85