Re: KASAN: vmalloc-out-of-bounds Write in imageblit

[Hao Sun]

Hi,

This bug can still be triggered repeatedly on the latest Linux.

HEAD commit: 519d81956ee2 Linux 5.15-rc6
git tree: upstream
console output:
https://drive.google.com/file/d/17xFIX8JgBxamy8iUnUTAdcVvaASuhqxr/view?usp=sharing
kernel config: https://drive.google.com/file/d/12PUnxIM1EPBgW4ZJmI7WJBRaY1lA83an/view?usp=sharing

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BUG: KASAN: vmalloc-out-of-bounds in fast_imageblit
drivers/video/fbdev/core/sysimgblt.c:229 [inline]
BUG: KASAN: vmalloc-out-of-bounds in sys_imageblit+0x1372/0x13f0
drivers/video/fbdev/core/sysimgblt.c:275
Write of size 4 at addr ffffc90005759380 by task syz-executor/31261

CPU: 2 PID: 31261 Comm: syz-executor Not tainted 5.15.0-rc6 #4
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.13.0-1ubuntu1.1 04/01/2014
Call Trace:
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
 print_address_description.constprop.0.cold+0xf/0x334 mm/kasan/report.c:256
 __kasan_report mm/kasan/report.c:442 [inline]
 kasan_report.cold+0x83/0xdf mm/kasan/report.c:459
 fast_imageblit drivers/video/fbdev/core/sysimgblt.c:229 [inline]
 sys_imageblit+0x1372/0x13f0 drivers/video/fbdev/core/sysimgblt.c:275
 drm_fb_helper_sys_imageblit+0x1c/0x180 drivers/gpu/drm/drm_fb_helper.c:794
 drm_fbdev_fb_imageblit+0x179/0x260 drivers/gpu/drm/drm_fb_helper.c:2282
 bit_putcs_unaligned drivers/video/fbdev/core/bitblit.c:139 [inline]
 bit_putcs+0x8ed/0xd80 drivers/video/fbdev/core/bitblit.c:188
 fbcon_putcs+0x362/0x450 drivers/video/fbdev/core/fbcon.c:1296
 do_update_region+0x399/0x630 drivers/tty/vt/vt.c:676
 invert_screen+0x2a7/0x610 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+0xda8/0x10a0 drivers/tty/vt/vt.c:1257
 fbcon_do_set_font+0x47e/0x780 drivers/video/fbdev/core/fbcon.c:2397
 fbcon_set_font+0x81e/0xa10 drivers/video/fbdev/core/fbcon.c:2483
 con_font_set drivers/tty/vt/vt.c:4666 [inline]
 con_font_op+0x73a/0xca0 drivers/tty/vt/vt.c:4710
 vt_k_ioctl drivers/tty/vt/vt_ioctl.c:474 [inline]
 vt_ioctl+0x1de9/0x2af0 drivers/tty/vt/vt_ioctl.c:752
 tty_ioctl+0xc80/0x1450 drivers/tty/tty_io.c:2805
 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: 0033:0x7ff832e3ec4d
Code: 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa 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 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ff8303a6c58 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ff832f650a0 RCX: 00007ff832e3ec4d
RDX: 0000000020000100 RSI: 0000000000004b72 RDI: 0000000000000004
RBP: 00007ff832eb7d80 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ff832f650a0
R13: 00007ffffdbaddff R14: 00007ffffdbadfa0 R15: 00007ff8303a6dc0


Memory state around the buggy address:
 ffffc90005759280: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
 ffffc90005759300: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
>ffffc90005759380: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
                   ^
 ffffc90005759400: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
 ffffc90005759480: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
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