kern/73719: Page fault in bpf_mtap ()
maxim at FreeBSD.org
Tue Nov 9 12:40:22 PST 2004
The following reply was made to PR kern/73719; it has been noted by GNATS.
From: Maxim Konovalov <maxim at FreeBSD.org>
To: Vladimir Ivanov <wawa at yandex-team.ru>
Cc: rwatson at FreeBSD.org, bug-followup at FreeBSD.org
Subject: Re: kern/73719: Page fault in bpf_mtap ()
Date: Tue, 9 Nov 2004 23:35:41 +0300 (MSK)
On Tue, 9 Nov 2004, 20:10-0000, Vladimir Ivanov wrote:
> The following reply was made to PR kern/73719; it has been noted by GNATS.
> From: Vladimir Ivanov <wawa at yandex-team.ru>
> To: freebsd-gnats-submit at FreeBSD.org, wawa at yandex-team.ru
> Subject: Re: kern/73719: Page fault in bpf_mtap ()
> Date: Tue, 09 Nov 2004 23:02:26 +0300
> The bpf_mtap () seems to be little enough to make a look.
> We suppose that most probable reason to panic is zero value of "bp" pointer.
> Also, I know that bpf open/close are frequent on my system.
> We can see (look at BPF_MTAP definition) that the value may be changed
> from another thread after verification but before bpf_mtap call because
> "ifp" points to global variable. The patch does not change the logic of
> program as you can see but garantee "bp" is not NULL. The only side
> effect is hypotetic pushing extra packet to just detached bpf device.
> It's not very big price I seem
> I've commited the patch to the system and awaiting results.
I can't believe this technique is a right way to fix things.
Robert, is bpf(4) MP safe already?
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