Re: Ugly rmap NULL ptr deref oopsie on hibernate (was Linux2.6.34-rc3)

From: Linus Torvalds
Date: Tue Apr 06 2010 - 12:58:21 EST

On Wed, 7 Apr 2010, Minchan Kim wrote:
> unmap_and_move
> remove_migration_ptes
> rmap_walk
> rmap_walk_anon
> We always has rcu_read_lock about anon page in unmap_and_move.
> So I think it's not buggy. What am I missing?

Ok, in that case it's fine.

However, it does bring back my comment about all those anonvma changes:
the locking is totally undocumented.

Why isn't there a thing _saying_ that it's ok because of this?

Why is there no comment about the locking of that 'same_vma' /
'vma->anon_vma_chain' except for the totally nonsensical one about
page_table_lock (which doesn't protect _any_ of the other cases)?

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