diff options
| author | Matthew Wilcox (Oracle) <willy@infradead.org> | 2024-11-25 20:17:18 +0000 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2024-12-05 19:54:45 -0800 |
| commit | 4de22b2a6a7477d84d9a01eb6b62a9117309d722 (patch) | |
| tree | b619660a80f68f1427cb0c9005004f1139970bf9 | |
| parent | d699440f58ce9bd71103cc7b692e3ab76a20bfcd (diff) | |
mm: open-code PageTail in folio_flags() and const_folio_flags()
It is unsafe to call PageTail() in dump_page() as page_is_fake_head() will
almost certainly return true when called on a head page that is copied to
the stack. That will cause the VM_BUG_ON_PGFLAGS() in const_folio_flags()
to trigger when it shouldn't. Fortunately, we don't need to call
PageTail() here; it's fine to have a pointer to a virtual alias of the
page's flag word rather than the real page's flag word.
Link: https://lkml.kernel.org/r/20241125201721.2963278-1-willy@infradead.org
Fixes: fae7d834c43c ("mm: add __dump_folio()")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Kees Cook <kees@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
| -rw-r--r-- | include/linux/page-flags.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 2220bfec278e..cf46ac720802 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -306,7 +306,7 @@ static const unsigned long *const_folio_flags(const struct folio *folio, { const struct page *page = &folio->page; - VM_BUG_ON_PGFLAGS(PageTail(page), page); + VM_BUG_ON_PGFLAGS(page->compound_head & 1, page); VM_BUG_ON_PGFLAGS(n > 0 && !test_bit(PG_head, &page->flags), page); return &page[n].flags; } @@ -315,7 +315,7 @@ static unsigned long *folio_flags(struct folio *folio, unsigned n) { struct page *page = &folio->page; - VM_BUG_ON_PGFLAGS(PageTail(page), page); + VM_BUG_ON_PGFLAGS(page->compound_head & 1, page); VM_BUG_ON_PGFLAGS(n > 0 && !test_bit(PG_head, &page->flags), page); return &page[n].flags; } |