On 3/30/21 5:31 PM, Andrey Konovalov wrote: > My commit "integrate page_alloc init with HW_TAGS" changed the order of > kernel_unpoison_pages() and kernel_init_free_pages() calls. This leads > to __GFP_ZERO allocations being incorrectly poisoned when page poisoning > is enabled. Correction: This leads to check_poison_mem() complain about memory corruption because the poison pattern has already been overwritten by zeroes. > Fix by restoring the initial order. Also add a warning comment. > > Reported-by: Vlastimil Babka <vbabka@xxxxxxx> > Reported-by: Sergei Trofimovich <slyfox@xxxxxxxxxx> > Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> I expect this will be folded to your patch in mmotm anyway, so the changelog is not as important... > --- > mm/page_alloc.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 033bd92e8398..1fc5061f8ca1 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -2328,6 +2328,12 @@ inline void post_alloc_hook(struct page *page, unsigned int order, > arch_alloc_page(page, order); > debug_pagealloc_map_pages(page, 1 << order); > > + /* > + * Page unpoisoning must happen before memory initialization. > + * Otherwise, a __GFP_ZERO allocation will not be initialized. ... but the comment should be corrected too: "Otherwise, a __GFP_ZERO allocation will trigger a memory corruption report during unpoisoning." Thanks. > + */ > + kernel_unpoison_pages(page, 1 << order); > + > /* > * As memory initialization might be integrated into KASAN, > * kasan_alloc_pages and kernel_init_free_pages must be > @@ -2338,7 +2344,6 @@ inline void post_alloc_hook(struct page *page, unsigned int order, > if (init && !kasan_has_integrated_init()) > kernel_init_free_pages(page, 1 << order); > > - kernel_unpoison_pages(page, 1 << order); > set_page_owner(page, order, gfp_flags); > } > >
