kern/73719: Page fault in bpf_mtap ()

Vladimir Ivanov wawa at
Tue Nov 9 12:10:31 PST 2004

The following reply was made to PR kern/73719; it has been noted by GNATS.

From: Vladimir Ivanov <wawa at>
To: freebsd-gnats-submit at, wawa at
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.

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