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

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: vmalloc-out-of-bounds Write in imageblit

==================================================================
BUG: KASAN: vmalloc-out-of-bounds in fast_imageblit drivers/video/fbdev/core/sysimgblt.c:257 [inline]
BUG: KASAN: vmalloc-out-of-bounds in sys_imageblit+0x1ed0/0x2240 drivers/video/fbdev/core/sysimgblt.c:323
Write of size 4 at addr ffffc90004411000 by task syz-executor.5/4188

CPU: 1 PID: 4188 Comm: syz-executor.5 Not tainted 5.19.0-rc8-syzkaller-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
Call Trace:
 <TASK>
 __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/0x495 mm/kasan/report.c:313
 print_report mm/kasan/report.c:429 [inline]
 kasan_report.cold+0xf4/0x1c6 mm/kasan/report.c:491
 fast_imageblit drivers/video/fbdev/core/sysimgblt.c:257 [inline]
 sys_imageblit+0x1ed0/0x2240 drivers/video/fbdev/core/sysimgblt.c:323
 drm_fb_helper_sys_imageblit drivers/gpu/drm/drm_fb_helper.c:825 [inline]
 drm_fbdev_fb_imageblit+0x15c/0x350 drivers/gpu/drm/drm_fb_helper.c:2328
 bit_putcs_unaligned drivers/video/fbdev/core/bitblit.c:139 [inline]
 bit_putcs+0x6e1/0xd20 drivers/video/fbdev/core/bitblit.c:188
 fbcon_putcs+0x314/0x3e0 drivers/video/fbdev/core/fbcon.c:1285
 do_update_region+0x399/0x630 drivers/tty/vt/vt.c:676
 redraw_screen+0x61f/0x740 drivers/tty/vt/vt.c:1035
 fbcon_do_set_font+0x5eb/0x6f0 drivers/video/fbdev/core/fbcon.c:2435
 fbcon_set_font+0x89d/0xab0 drivers/video/fbdev/core/fbcon.c:2522
 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+0x1efa/0x2b20 drivers/tty/vt/vt_ioctl.c:752
 tty_ioctl+0xbbd/0x15e0 drivers/tty/tty_io.c:2778
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl fs/ioctl.c:856 [inline]
 __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:856
 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+0x63/0xcd
RIP: 0033:0x7fb2a0689109
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fb2a1830168 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fb2a079bf60 RCX: 00007fb2a0689109
RDX: 0000000020000040 RSI: 0000000000004b72 RDI: 0000000000000004
RBP: 00007fb2a18301d0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffca595479f R14: 00007fb2a1830300 R15: 0000000000022000
 </TASK>

The buggy address belongs to the virtual mapping at
 [ffffc90004111000, ffffc90004412000) created by:
 drm_gem_shmem_vmap_locked drivers/gpu/drm/drm_gem_shmem_helper.c:319 [inline]
 drm_gem_shmem_vmap+0x3d7/0x5a0 drivers/gpu/drm/drm_gem_shmem_helper.c:366

Memory state around the buggy address:
 ffffc90004410f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc90004410f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffc90004411000: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
                   ^
 ffffc90004411080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
 ffffc90004411100: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
==================================================================


Tested on:

commit:         e0dccc3b Linux 5.19-rc8
git tree:       https://github.com/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=13963ed2080000
kernel config:  https://syzkaller.appspot.com/x/.config?x=26034e6fe0075dad
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
patch:          https://syzkaller.appspot.com/x/patch.diff?x=14d7b5da080000