Crash in VirtualBox virtual machines running kernel 6.5

[Larry Finger]

Hi,

When I try to start a VirtualBox virtual machine running kernel 6.5-rc2, it gets 
a kernel bug as follows while trying to mount a vboxsf-shared mount:

Jul 19 08:48:19 localhost kernel: detected buffer overflow in strscpy
Jul 19 08:48:19 localhost kernel: ------------[ cut here ]------------
Jul 19 08:48:19 localhost kernel: kernel BUG at lib/string_helpers.c:1031!
Jul 19 08:48:19 localhost kernel: invalid opcode: 0000 [#1] PREEMPT SMP PTI
Jul 19 08:48:19 localhost kernel: CPU: 2 PID: 507 Comm: mount.vboxsf Not tainted 
6.5.0-rc2-1.gc159bc5-default #1 openSUSE Tumbleweed (unreleased) 
4ec79f0435e04b515527e428ee3d62093b7f6e02
Jul 19 08:48:19 localhost kernel: Hardware name: innotek GmbH 
VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
Jul 19 08:48:19 localhost kernel: RIP: 0010:fortify_panic+0x13/0x20
Jul 19 08:48:19 localhost kernel: Code: 41 5d c3 cc cc cc cc 90 90 90 90 90 90 
90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 48 89 fe 48 c7 c7 68 e5 c6 93 e8 ed a7 
b2 ff <0f> 0b 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90
Jul 19 08:48:19 localhost kernel: RSP: 0018:ffffa72a4047fd40 EFLAGS: 00010246
Jul 19 08:48:19 localhost kernel: RAX: 0000000000000023 RBX: ffff903ac9d8ac00 
RCX: 0000000000000000
Jul 19 08:48:19 localhost kernel: RDX: 0000000000000000 RSI: ffff903adbd274c0 
RDI: ffff903adbd274c0
Jul 19 08:48:19 localhost kernel: RBP: 0000000000000002 R08: 0000000000000000 
R09: ffffa72a4047fc00
Jul 19 08:48:19 localhost kernel: R10: 0000000000000003 R11: ffffffff94558568 
R12: ffff903ac2013f00
Jul 19 08:48:19 localhost kernel: R13: ffff903ac8492800 R14: ffff903ac7b9dd20 
R15: 0000000000000007
Jul 19 08:48:19 localhost kernel: FS:  00007f22f0cec740(0000) 
GS:ffff903adbd00000(0000) knlGS:0000000000000000
Jul 19 08:48:19 localhost kernel: CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Jul 19 08:48:19 localhost kernel: CR2: 00007f22f0e7f574 CR3: 0000000109474001 
CR4: 00000000000706e0
Jul 19 08:48:19 localhost kernel: Call Trace:
Jul 19 08:48:19 localhost kernel:  <TASK>
Jul 19 08:48:19 localhost kernel:  ? die+0x36/0x90
Jul 19 08:48:19 localhost kernel:  ? do_trap+0xda/0x100
Jul 19 08:48:19 localhost kernel:  ? fortify_panic+0x13/0x20
Jul 19 08:48:19 localhost kernel:  ? do_error_trap+0x6a/0x90
Jul 19 08:48:19 localhost kernel:  ? fortify_panic+0x13/0x20
Jul 19 08:48:19 localhost kernel:  ? exc_invalid_op+0x50/0x70
Jul 19 08:48:19 localhost kernel:  ? fortify_panic+0x13/0x20
Jul 19 08:48:19 localhost kernel:  ? asm_exc_invalid_op+0x1a/0x20
Jul 19 08:48:19 localhost kernel:  ? fortify_panic+0x13/0x20
Jul 19 08:48:19 localhost kernel:  vboxsf_fill_super+0x3bc/0x3c0 [vboxsf 
447dff7257fbc53f0b47ed873d2b02eb4773401c]
Jul 19 08:48:19 localhost kernel:  ? __pfx_vboxsf_fill_super+0x10/0x10 [vboxsf 
447dff7257fbc53f0b47ed873d2b02eb4773401c]
Jul 19 08:48:19 localhost kernel:  vfs_get_super+0x6e/0xe0
Jul 19 08:48:19 localhost kernel:  vfs_get_tree+0x29/0xd0
Jul 19 08:48:19 localhost kernel:  path_mount+0x491/0xac0
Jul 19 08:48:19 localhost kernel:  __x64_sys_mount+0x109/0x140
Jul 19 08:48:19 localhost kernel:  do_syscall_64+0x60/0x90
Jul 19 08:48:19 localhost kernel:  ? count_memcg_events.constprop.0+0x1a/0x30
Jul 19 08:48:19 localhost kernel:  ? handle_mm_fault+0x9e/0x350
Jul 19 08:48:19 localhost kernel:  ? do_user_addr_fault+0x225/0x640
Jul 19 08:48:19 localhost kernel:  ? exc_page_fault+0x71/0x160
Jul 19 08:48:19 localhost kernel:  entry_SYSCALL_64_after_hwframe+0x6e/0xd8
Jul 19 08:48:19 localhost kernel: RIP: 0033:0x7f22f0e05b9e
Jul 19 08:48:19 localhost kernel: Code: c3 66 2e 0f 1f 84 00 00 00 00 00 90 90 
90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 49 89 ca b8 a5 00 00 00 
0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 3a 02 0d 00 f7 d8 64 89 01 48
Jul 19 08:48:19 localhost kernel: RSP: 002b:00007ffe8ba4bab8 EFLAGS: 00000212 
ORIG_RAX: 00000000000000a5
Jul 19 08:48:19 localhost kernel: RAX: ffffffffffffffda RBX: 00007ffe8ba4df04 
RCX: 00007f22f0e05b9e
Jul 19 08:48:19 localhost kernel: RDX: 000055e9ab199ba8 RSI: 00007ffe8ba4df0b 
RDI: 00007ffe8ba4df04
Jul 19 08:48:19 localhost kernel: RBP: 00007ffe8ba4bc00 R08: 00007ffe8ba4bf50 
R09: 0000000000000000
Jul 19 08:48:19 localhost kernel: R10: 0000000000000004 R11: 0000000000000212 
R12: 00007ffe8ba4df0b
Jul 19 08:48:19 localhost kernel: R13: 0000000000000011 R14: 00007ffe8ba4bf50 
R15: 00007ffe8ba4df29
Jul 19 08:48:19 localhost kernel:  </TASK>
Jul 19 08:48:19 localhost kernel: Modules linked in: vboxsf vboxguest fuse 
efi_pstore configfs dmi_sysfs ip_tables x_tables crct10dif_pclmul crc32_pclmul 
polyval_clmulni polyval_generic sr_mod ohci_pci gf128mul cdrom ohci_hcd ehci_pci 
ehci_hcd ghash_clmulni_intel sha512_ssse3 ata_generic vmwgfx video usbcore 
drm_ttm_helper ttm aesni_intel crypto_simd cryptd ata_piix wmi serio_raw btrfs 
blake2b_generic libcrc32c crc32c_intel xor raid6_pq sg dm_multipath dm_mod 
scsi_dh_rdac scsi_dh_emc scsi_dh_alua msr efivarfs
Jul 19 08:48:19 localhost kernel: ---[ end trace 0000000000000000 ]---

The traceback points to the strscpy() added in commit 883f8fe87686d, which 
ironically was submitted to avoid buffer overflows using strlcpy(); however, I 
do not think that is the problem. My suspicion is that it comes from struct 
shfl_string, and the definition of the variable-length arrays in the union, and 
that their lengths are confusing the kernel's string handling routines.

I will be happy to test any proposed patches.

Larry