Commit f165b378 authored by Pavel Tatashin's avatar Pavel Tatashin Committed by Linus Torvalds
Browse files

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@oracle.com: v4]
  Link: http://lkml.kernel.org/r/20180215165920.8570-4-pasha.tatashin@oracle.com
Link: http://lkml.kernel.org/r/20180213193159.14606-4-pasha.tatashin@oracle.com


Signed-off-by: default avatarPavel Tatashin <pasha.tatashin@oracle.com>
Reviewed-by: default avatarIngo Molnar <mingo@kernel.org>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Bharata B Rao <bharata@linux.vnet.ibm.com>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Steven Sistare <steven.sistare@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 078eb6aa

include/linux/mm.h

+3 −1
Original line number Diff line number Diff line
@@ -903,7 +903,9 @@ extern int page_to_nid(const struct page *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

include/linux/page-flags.h

+17 −5
Original line number Diff line number Diff line
@@ -156,9 +156,18 @@ static __always_inline int PageCompound(struct page *page) 
	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(struct page *page) 
 * 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

mm/memblock.c

+1 −1
Original line number Diff line number Diff line
@@ -1345,7 +1345,7 @@ void * __init memblock_virt_alloc_try_nid_raw( 
					   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;

}

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