Kernel panic in nfsv4_loadattr

[Fabian Freyer]

Hi!

I've had a panic on a host mounting NFSv4 shares. There are also jails
running on this host acessing these shares (I assume this might be a
problem, as I'm also seeing the nfsuserd messages mentioned in [1]).
Here's the last relevant lines of the kernel message buffer:


-----8< [snip]

Jun 25 05:47:39 emmi nfsuserd:[916]: req from ip=0x[REDACTED] port=949
kernel trap 12 with interrupts disabled


Fatal trap 12: page fault while in kernel mode
cpuid = 4; apic id = 04
fault virtual address   = 0x2418
fault code              = supervisor read data, page not present
instruction pointer     = 0x20:0xffffffff80ab5598
stack pointer           = 0x28:0xfffffe104bfd4740
frame pointer           = 0x28:0xfffffe104bfd47a0
code segment            = base 0x0, limit 0xfffff, type 0x1b
                        = DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags        = resume, IOPL = 0
current process         = 11790 (pop3)
trap number             = 12
panic: page fault
cpuid = 4
KDB: stack backtrace:
#0 0xffffffff80b24477 at kdb_backtrace+0x67
#1 0xffffffff80ad97e2 at vpanic+0x182
#2 0xffffffff80ad9653 at panic+0x43
#3 0xffffffff80fa1d51 at trap_fatal+0x351
#4 0xffffffff80fa1f43 at trap_pfault+0x1e3
#5 0xffffffff80fa14ec at trap+0x26c
#6 0xffffffff80f845a1 at calltrap+0x8
#7 0xffffffff80b39cb9 at propagate_priority+0xb9
#8 0xffffffff80b3a99f at turnstile_wait+0x3ef
#9 0xffffffff80ad4764 at __rw_wlock_hard+0x94
#10 0xffffffff80d0b0af at udp_disconnect+0x9f
#11 0xffffffff80b728cc at soclose+0x3c
#12 0xffffffff80d7ce84 at clnt_dg_destroy+0x2f4
#13 0xffffffff80d7deae at clnt_reconnect_call+0x8be
#14 0xffffffff80993ead at newnfs_request+0xa6d
#15 0xffffffff8099d894 at nfsrv_getuser+0x234
#16 0xffffffff8099b939 at nfsv4_strtogid+0x259
#17 0xffffffff8099a323 at nfsv4_loadattr+0x3713
Uptime: 19d17h29m20s

-----8< [snap]

I'm a bit unsure as to how to debug this. This is the second time this
crash has happened (last time 19 days ago...) so it's somewhat
reproducable. I'd be happy about any pointers.

Fabian

[1] https://lists.freebsd.org/pipermail/freebsd-fs/2016-December/024259.html

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