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SubjectRe: [PATCH] mm: fix lazy vmap purging (use-after-free error)
On Fri, Feb 20, 2009 at 03:01:57PM +0100, Ingo Molnar wrote:
>
> * Ingo Molnar <mingo@elte.hu> 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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