kernel warning in validstat

Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported
kernel warning in statcheck	C			846880	2250d	2313d
яkernel warning at kern/src/ns/convM2D.c:52, from core 1: яnbuf 27, STAT_FIX_LEN_9P 49 BIT16SZ 2, GBIT16(buf) 0  
пїЅStack Backtrace on Core 1:
пїЅ#01 [<0xffffffffc200a2dc>] in backtrace
#02 [<0xffffffffc2009b94>] in _warn
пїЅ#03 [<0xffffffffc2034c0d>]9P in 2000statcheck
#04 [<0xffffffffc203deb8>] in validstat at src/ns/sysfile.c:961
#05 [<0xffffffffc203ef1e>] in sysfwstat at src/ns/sysfile.c:421
#06 [<0xffffffffc2055c70>] in sys_fwstat at src/syscall.c:2337
#07 [<0xffffffffc2059409>] in syscall at src/syscall.c:2528
#08 [<0xffffffffc20595d4>] in run_local_syscall at src/syscall.c:2563
#09 [<0xffffffffc2059b09>] in prep_syscalls at src/syscall.c:2583
#10 [<0xffffffffc20ab36a>] in sysenter_callwrapper at arch/x86/trap.c:854
Core 00, prov: 0(0x0000000000000000) alloc: 0(0x0000000000000000)
kernel panic at kern/arch/x86/trap.c:312, from core 2: Proc-ful Page Fault in the Kernel at 0x0000000000000000!
HW TRAP frame at 0xfffffff0000b2620 on core 2
  rax  0x0000000000000000
  rbx  0xffffffffc210f658
  rcx  0xffff80000486ce10
  rdx  0x0000000000000002
  rbp  0xfffffff0000b2748
  rsi  0xffffffffc210f640
  rdi  0xffffffffc210f658
  r8   0x0000000000000000
  r9   0x000000000000000d
  r10  0x0000000000000020
  r11  0x000000000000000a
  r12  0x0000000000000000
  r13  0xffffffffc20b1b00
  r14  0xffff800016229220
  r15  0xffffffffc210f640
  trap 0x0000000e Page Fault
  gsbs 0xffffffffc8667ec0
  fsbs 0x0000000000000000
  err  0x--------00000002
  rip  0xffffffffc200be1c
  cs   0x------------0008
  flag 0x0000000000010086
  rsp  0xfffffff0000b26e8
  ss   0x------------0010
Backtrace of kernel context on Core 2:
#01 [<0xffffffffc200be1c>] in sem_down at src/kthread.c:434
#02 [<0xffffffffc2076054>] in consread at drivers/dev/cons.c:815
#03 [<0xffffffffc207d4e2>] in mntversion at drivers/dev/mnt.c:223
#04 [<0xffffffffc207e882>] in mntattach at drivers/dev/mnt.c:356
#05 [<0xffffffffc203f221>] in sysmount at src/ns/sysfile.c:528
#06 [<0xffffffffc2055b11>] in sys_nmount at src/syscall.c:2259
#07 [<0xffffffffc2059409>] in syscall at src/syscall.c:2528
#08 [<0xffffffffc20595d4>] in run_local_syscall at src/syscall.c:2563
#09 [<0xffffffffc2059b09>] in prep_syscalls at src/syscall.c:2583
#10 [<0xffffffffc20ab36a>] in sysenter_callwrapper at arch/x86/trap.c:854
Core 01, prov: 0(0x0000000000000000) alloc: 78(0xffff800016626c40)
Core 02, prov: 0(0x0000000000000000) alloc: 77(0xffff800016627b80)
Core 03, prov: 0(0x0000000000000000) alloc: 75(0xffff800002174000)