Re: panic: mb_dtor_pack: ref_cnt != 1

Andre Oppermann wrote:
> Kris Kennaway wrote:
> 
>> I got this panic shortly after boot on a freshly-updated amd64
>> machine:
>>
>> FreeBSD/amd64 (fbsd-amd64.isc.org) (ttyd0)
>>
>> login: panic: mb_dtor_pack: ref_cnt != 1
>> cpuid = 3
>> KDB: enter: panic
>> [thread pid 1021 tid 100131 ]
>> Stopped at      kdb_enter+0x31: leave
>> db> wh
>> Tracing pid 1021 tid 100131 td 0xffffff0323816a40
>> kdb_enter() at kdb_enter+0x31
>> panic() at panic+0x1e6
>> mb_dtor_pack() at mb_dtor_pack+0x103
>> uma_zfree_arg() at uma_zfree_arg+0x34
>> mb_free_ext() at mb_free_ext+0xe9
>> soreceive() at soreceive+0xafb
>> soo_read() at soo_read+0x5e
>> dofileread() at dofileread+0x9e
>> kern_readv() at kern_readv+0x4f
>> read() at read+0x4b
>> syscall() at syscall+0x350
>> Xfast_syscall() at Xfast_syscall+0xa8
>> --- syscall (3, FreeBSD ELF64, read), rip = 0x800b7e23c, rsp = 
>> 0x7fffffffe1a8, rbp = 0x400 ---
> 
> There is some modify-after-free going on with that mbuf cluster.
> The mandatory mbuf cluster refcounting bringing it to the light.
> 
> Something is smelly in the socket buffer code and we have to out
> what exactly goes wrong.

Actually it's a logic bug in the mb_free_ext() code.  Damn.  Patch
in an hour.

-- 
Andre