The patch titled Subject: mm: open-code page_folio() in dump_page() has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-open-code-page_folio-in-dump_page.patch
This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...
This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------ From: "Matthew Wilcox (Oracle)" willy@infradead.org Subject: mm: open-code page_folio() in dump_page() Date: Mon, 25 Nov 2024 20:17:19 +0000
page_folio() calls page_fixed_fake_head() which will misidentify this page as being a fake head and load off the end of 'precise'. We may have a pointer to a fake head, but that's OK because it contains the right information for dump_page().
gcc-15 is smart enough to catch this with -Warray-bounds:
In function 'page_fixed_fake_head', inlined from '_compound_head' at ../include/linux/page-flags.h:251:24, inlined from '__dump_page' at ../mm/debug.c:123:11: ../include/asm-generic/rwonce.h:44:26: warning: array subscript 9 is outside +array bounds of 'struct page[1]' [-Warray-bounds=]
Link: https://lkml.kernel.org/r/20241125201721.2963278-2-willy@infradead.org Fixes: fae7d834c43c ("mm: add __dump_folio()") Signed-off-by: Matthew Wilcox (Oracle) willy@infradead.org Reported-by: Kees Cook kees@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
mm/debug.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
--- a/mm/debug.c~mm-open-code-page_folio-in-dump_page +++ a/mm/debug.c @@ -124,19 +124,22 @@ static void __dump_page(const struct pag { struct folio *foliop, folio; struct page precise; + unsigned long head; unsigned long pfn = page_to_pfn(page); unsigned long idx, nr_pages = 1; int loops = 5;
again: memcpy(&precise, page, sizeof(*page)); - foliop = page_folio(&precise); - if (foliop == (struct folio *)&precise) { + head = precise.compound_head; + if ((head & 1) == 0) { + foliop = (struct folio *)&precise; idx = 0; if (!folio_test_large(foliop)) goto dump; foliop = (struct folio *)page; } else { + foliop = (struct folio *)(head - 1); idx = folio_page_idx(foliop, page); }
_
Patches currently in -mm which might be from willy@infradead.org are
mm-open-code-pagetail-in-folio_flags-and-const_folio_flags.patch mm-open-code-page_folio-in-dump_page.patch mm-page_alloc-cache-page_zone-result-in-free_unref_page.patch mm-make-alloc_pages_mpol-static.patch mm-page_alloc-export-free_frozen_pages-instead-of-free_unref_page.patch mm-page_alloc-move-set_page_refcounted-to-callers-of-post_alloc_hook.patch mm-page_alloc-move-set_page_refcounted-to-callers-of-prep_new_page.patch mm-page_alloc-move-set_page_refcounted-to-callers-of-get_page_from_freelist.patch mm-page_alloc-move-set_page_refcounted-to-callers-of-__alloc_pages_cpuset_fallback.patch mm-page_alloc-move-set_page_refcounted-to-callers-of-__alloc_pages_may_oom.patch mm-page_alloc-move-set_page_refcounted-to-callers-of-__alloc_pages_direct_compact.patch mm-page_alloc-move-set_page_refcounted-to-callers-of-__alloc_pages_direct_reclaim.patch mm-page_alloc-move-set_page_refcounted-to-callers-of-__alloc_pages_slowpath.patch mm-page_alloc-move-set_page_refcounted-to-end-of-__alloc_pages.patch mm-page_alloc-add-__alloc_frozen_pages.patch mm-mempolicy-add-alloc_frozen_pages.patch slab-allocate-frozen-pages.patch