On Thu, Sep 26, 2024 at 05:42:34PM +0200, David Hildenbrand wrote: > We should only check for pmd_special() after we made sure that we > have a present PMD. For example, if we have a migration PMD, > pmd_special() might indicate that we have a special PMD although we > really don't. > > This fixes confusing migration entries as PFN mappings, and not > doing what we are supposed to do in the "is_swap_pmd()" case further > down in the function -- including messing up COW, page table handling > and accounting. > > Reported-by: syzbot+bf2c35fa302ebe3c7471@xxxxxxxxxxxxxxxxxxxxxxxxx > Closes: https://lore.kernel.org/lkml/66f15c8d.050a0220.c23dd.000f.GAE@xxxxxxxxxx/ > Fixes: bc02afbd4d73 ("mm/fork: accept huge pfnmap entries") > Cc: Peter Xu <peterx@xxxxxxxxxx> > Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> Reviewed-by: Peter Xu <peterx@xxxxxxxxxx> -- Peter Xu
