Re: [PATCH] mm: fix lazy vmap purging (use-after-free error)

[Paul E. McKenney]

On Fri, Feb 20, 2009 at 03:01:57PM +0100, Ingo Molnar wrote:
> 
> * Ingo Molnar <mingo@xxxxxxx> wrote:
> 
> > ah, indeed:
> > 
> >         list_del_rcu(&va->list);
> > 
> > i suspect it could be hit big time in a workload that opens 
> > more than 512 files, as expand_files() uses a 
> > vmalloc()+vfree() pair in that case.
> 
> hm, perhaps it's not a problem after all. The freeing is done 
> via rcu, and list_del_rcu() leaves the forward pointer intact.
> 
> So how did it happen that the entry got kfree()d before the loop 
> was done? We are in a spinlocked section so the CPU should not 
> have entered rcu processing.

Good point -- is the .config file available?

							Thanx, Paul
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