From: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> Subject: mm: uninitialized struct page poisoning sanity checking During boot we poison struct page memory in order to ensure that no one is accessing this memory until the struct pages are initialized in __init_single_page(). This patch adds more scrutiny to this checking by making sure that flags do not equal the poison pattern when they are accessed. The pattern is all ones. Since node id is also stored in struct page, and may be accessed quite early, we add this enforcement into page_to_nid() function as well. Note, this is applicable only when NODE_NOT_IN_PAGE_FLAGS=n [pasha.tatashin@xxxxxxxxxx: v4] Link: http://lkml.kernel.org/r/20180215165920.8570-4-pasha.tatashin@xxxxxxxxxx Link: http://lkml.kernel.org/r/20180213193159.14606-4-pasha.tatashin@xxxxxxxxxx Signed-off-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> Reviewed-by: Ingo Molnar <mingo@xxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Cc: Baoquan He <bhe@xxxxxxxxxx> Cc: Bharata B Rao <bharata@xxxxxxxxxxxxxxxxxx> Cc: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx> Cc: Dan Williams <dan.j.williams@xxxxxxxxx> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> Cc: Steven Sistare <steven.sistare@xxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/mm.h | 4 +++- include/linux/page-flags.h | 22 +++++++++++++++++----- mm/memblock.c | 2 +- 3 files changed, 21 insertions(+), 7 deletions(-) diff -puN include/linux/mm.h~mm-uninitialized-struct-page-poisoning-sanity-checking include/linux/mm.h --- a/include/linux/mm.h~mm-uninitialized-struct-page-poisoning-sanity-checking +++ a/include/linux/mm.h @@ -903,7 +903,9 @@ extern int page_to_nid(const struct page #else static inline int page_to_nid(const struct page *page) { - return (page->flags >> NODES_PGSHIFT) & NODES_MASK; + struct page *p = (struct page *)page; + + return (PF_POISONED_CHECK(p)->flags >> NODES_PGSHIFT) & NODES_MASK; } #endif diff -puN include/linux/page-flags.h~mm-uninitialized-struct-page-poisoning-sanity-checking include/linux/page-flags.h --- a/include/linux/page-flags.h~mm-uninitialized-struct-page-poisoning-sanity-checking +++ a/include/linux/page-flags.h @@ -156,9 +156,18 @@ static __always_inline int PageCompound( return test_bit(PG_head, &page->flags) || PageTail(page); } +#define PAGE_POISON_PATTERN -1l +static inline int PagePoisoned(const struct page *page) +{ + return page->flags == PAGE_POISON_PATTERN; +} + /* * Page flags policies wrt compound pages * + * PF_POISONED_CHECK + * check if this struct page poisoned/uninitialized + * * PF_ANY: * the page flag is relevant for small, head and tail pages. * @@ -176,17 +185,20 @@ static __always_inline int PageCompound( * PF_NO_COMPOUND: * the page flag is not relevant for compound pages. */ -#define PF_ANY(page, enforce) page -#define PF_HEAD(page, enforce) compound_head(page) +#define PF_POISONED_CHECK(page) ({ \ + VM_BUG_ON_PGFLAGS(PagePoisoned(page), page); \ + page; }) +#define PF_ANY(page, enforce) PF_POISONED_CHECK(page) +#define PF_HEAD(page, enforce) PF_POISONED_CHECK(compound_head(page)) #define PF_ONLY_HEAD(page, enforce) ({ \ VM_BUG_ON_PGFLAGS(PageTail(page), page); \ - page;}) + PF_POISONED_CHECK(page); }) #define PF_NO_TAIL(page, enforce) ({ \ VM_BUG_ON_PGFLAGS(enforce && PageTail(page), page); \ - compound_head(page);}) + PF_POISONED_CHECK(compound_head(page)); }) #define PF_NO_COMPOUND(page, enforce) ({ \ VM_BUG_ON_PGFLAGS(enforce && PageCompound(page), page); \ - page;}) + PF_POISONED_CHECK(page); }) /* * Macros to create function definitions for page flags diff -puN mm/memblock.c~mm-uninitialized-struct-page-poisoning-sanity-checking mm/memblock.c --- a/mm/memblock.c~mm-uninitialized-struct-page-poisoning-sanity-checking +++ a/mm/memblock.c @@ -1345,7 +1345,7 @@ void * __init memblock_virt_alloc_try_ni min_addr, max_addr, nid); #ifdef CONFIG_DEBUG_VM if (ptr && size > 0) - memset(ptr, 0xff, size); + memset(ptr, PAGE_POISON_PATTERN, size); #endif return ptr; } _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
