Re: + mm-madvise-fix-freeing-of-locked-page-with-madv_free.patch added to -mm tree

[Nadav Amit]

Michal Hocko <mhocko@xxxxxxxxxx> wrote:

> Hmm, I do not see this neither in linux-mm nor LKML. Strange
> 
> On Wed 23-08-17 14:41:21, Andrew Morton wrote:
>> From: Eric Biggers <ebiggers@xxxxxxxxxx>
>> Subject: mm/madvise.c: fix freeing of locked page with MADV_FREE
>> 
>> If madvise(..., MADV_FREE) split a transparent hugepage, it called
>> put_page() before unlock_page().  This was wrong because put_page() can
>> free the page, e.g.  if a concurrent madvise(..., MADV_DONTNEED) has
>> removed it from the memory mapping.  put_page() then rightfully complained
>> about freeing a locked page.
>> 
>> Fix this by moving the unlock_page() before put_page().

Quick grep shows that a similar flow (put_page() followed by an
unlock_page() ) also happens in hugetlbfs_fallocate(). Isnât it a problem as
well?