netdev - Re: [PATCH][RFC] Check sk

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Message-Id: <EB1E9C2D-55C5-4B57-A98D-E195309E9E05@earthlink.net>
Date:	Mon, 7 Jun 2010 21:46:10 -0700
From:	Mitchell Erblich <erblichs@...thlink.net>
To:	David VomLehn <dvomlehn@...co.com>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH][RFC] Check sk_buff states


On Jun 7, 2010, at 5:30 PM, David VomLehn wrote:

> This uses the oobparam and callsite infrastructure to implement sk_buff
> state checking and error reporting. Possible states of an sk_buff are:
> 	SKB_STATE_FREE - Is not currently in use
> 	SKB_STATE_ALLOCATED - Has been allocated, but is not on a queue
> 	SKB_STATE_QUEUED - Is allocated and on a queue
> Since there are only three states, two bits suffice to record the state of
> an sk_buff structure, so checking for consistent state is easy. (For you
> weenies, the fourth possible state *is* flagged as an error).


... cut...

Just my two cents,
Just initially thinking of the state names & using only two bits
If a 3rd bit, then it could indicate exclusive or shared (double free then acceptable if shared)

kmem_alloc, malloc, etc actually allocate structs
when something is allocated but not associated with anything, then it has no reference

so then why not?

xxx_STATE_INVALID:		both bits unset
xxx_STATE_ALLOCATED:     bit 0 set and bit 1 not set
xxx_STATE_REFERENCED : could be exclusive or shared, bit 0 unset & bit 1 set
xxx_STATE_QUEUED:           both bits set

Mitchell Erblich



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