cvs commit: src/sys/dev/io iodev.c

[John Baldwin]

On Tuesday 12 August 2008 10:07:43 am Bruce Evans wrote:
> I checked that bpf panics (even under UP) due to the obvious bugs in
> its d_close():
> 
>      # Generate lots of network activity using something like:
>      sysctl net.inet.icmp.icmplim=0; ping -fq localhost &
> 
>      # Race to panic eventually:
>      while :; do tcpdump -i lo0 & sleep 0.001; revoke /dev/bpf0
> 
> Most or all device drivers have obvious bugs in their d_close(); bpf
> is just a bit easier to understand and more likely to cause a panic
> than most device drivers, since it is simple and frees resources.  A
> panic is very likely when si_drv1 is freed, and si_drv1 is only locked
> accidentally.

I think revoke(2) should EINVAL (or ENOTTY) for non-ttys.  Of course bpf is 
broken with revoke, but nobody uses revoke with bpf.  What people do do in 
the normal course of using bpf is lots of concurrent bpf accesses, and w/o 
D_TRACKCLOSE, bpf devices don't get closed.

-- 
John Baldwin