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authorRalph Campbell <rcampbell@nvidia.com>2020-10-13 16:56:00 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-10-13 18:38:33 -0700
commita9b576f7253e22528584f5aeb46edf0b6b007992 (patch)
tree8330e51264c87e3be6efe80cf546a470ad83605a /mm/swap.c
parent30d8ec73e8772b32a7eae626d14004bd37d8f13c (diff)
mm: move call to compound_head() in release_pages()
The function is_huge_zero_page() doesn't call compound_head() to make sure the page pointer is a head page. The call to is_huge_zero_page() in release_pages() is made before compound_head() is called so the test would fail if release_pages() was called with a tail page of the huge_zero_page and put_page_testzero() would be called releasing the page. This is unlikely to be happening in normal use or we would be seeing all sorts of process data corruption when accessing a THP zero page. Looking at other places where is_huge_zero_page() is called, all seem to only pass a head page so I think the right solution is to move the call to compound_head() in release_pages() to a point before calling is_huge_zero_page(). Signed-off-by: Ralph Campbell <rcampbell@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Yu Zhao <yuzhao@google.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Christoph Hellwig <hch@lst.de> Link: https://lkml.kernel.org/r/20200917173938.16420-1-rcampbell@nvidia.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/swap.c')
-rw-r--r--mm/swap.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/swap.c b/mm/swap.c
index f41ccd8eae94..47a47681c86b 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -889,6 +889,7 @@ void release_pages(struct page **pages, int nr)
locked_pgdat = NULL;
}
+ page = compound_head(page);
if (is_huge_zero_page(page))
continue;
@@ -910,7 +911,6 @@ void release_pages(struct page **pages, int nr)
}
}
- page = compound_head(page);
if (!put_page_testzero(page))
continue;