cvs commit: src/sys/net if_vlan.c

[Yar Tikhiy]

On Thu, Jun 29, 2006 at 01:24:56PM +0400, Maxim Konovalov wrote:
> On Thu, 29 Jun 2006, 07:52-0000, Yar Tikhiy wrote:
> 
> > yar         2006-06-29 07:52:30 UTC
> >
> >   FreeBSD src repository
> >
> >   Modified files:
> >     sys/net              if_vlan.c
> >   Log:
> >   Detach the interface first, do vlan_unconfig() then.
> >   Previously, another thread could get a pointer to the
> >   interface by scanning the system-wide list and sleep
> >   on the global vlan mutex held by vlan_unconfig().
> >   The interface was gone by the time the other thread
> >   woke up.
> >
> >   In order to be able to call vlan_unconfig() on a detached
> >   interface, remove the purely cosmetic bzero'ing of IF_LLADDR
> >   from the function because a detached interface has no addresses.
> >
> >   Noticed by:     a stress-testing script by maxim
> >   Reviewed by:    glebius
> 
> Still no cookie :-)
> 
> db> bt
> Tracing pid 75800 tid 100098 td 0xc2b0e960
> in_control(c2a1c67c,c02069f6,c40eece0,c2e66000,c2b0e960) at in_control+0x114
> ifioctl(c2a1c67c,c02069f6,c40eece0,c2b0e960,0,...) at ifioctl+0xee
> soo_ioctl(c27cb4c8,c02069f6,c40eece0,c2c04980,c2b0e960) at soo_ioctl+0x2db
> ioctl(c2b0e960,d56a4d04) at ioctl+0x370
> syscall(3b,3b,3b,bfbfe2c4,0,...) at syscall+0x27e
> Xint0x80_syscall() at Xint0x80_syscall+0x1f
> --- syscall (54, FreeBSD ELF32, ioctl), eip = 0x2817cb43, esp =
> 0xbfbfe28c, ebp = 0xbfbfe2d8 ---
> 
> Let me know if you need more info.

I stress tested gif(4) in the same manner for kicks and got a very
similar panic in in_control().  I suppose that my change eliminated
a concurrency problem in vlan(4) and we began to feel the lack of
refcounting at ifnet level.  Indeed, a thread can keep a pointer
to an ifnet beyond its lifetime and panic the system on access to
the dead ifnet.

-- 
Yar