diff options
| author | Laura Abbott <labbott@fedoraproject.org> | 2016-03-15 14:56:30 -0700 |
|---|---|---|
| committer | Vinayak Menon <vinmenon@codeaurora.org> | 2017-04-14 23:43:04 +0530 |
| commit | 2c00b603db67af40aa0b02c834cc58fec98d3023 (patch) | |
| tree | dcf7d9ea21e05af4e35dc59837811da8ff0a2b43 /mm/page_alloc.c | |
| parent | 5c69adad61e27f467fa8e1671633e455741e3fae (diff) | |
mm/page_poisoning.c: allow for zero poisoning
By default, page poisoning uses a poison value (0xaa) on free. If this
is changed to 0, the page is not only sanitized but zeroing on alloc
with __GFP_ZERO can be skipped as well. The tradeoff is that detecting
corruption from the poisoning is harder to detect. This feature also
cannot be used with hibernation since pages are not guaranteed to be
zeroed after hibernation.
Credit to Grsecurity/PaX team for inspiring this work
Change-Id: If7116e6bff246abbafc38bdfeb3601d3ea063ad2
Signed-off-by: Laura Abbott <labbott@fedoraproject.org>
Acked-by: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Mathias Krause <minipli@googlemail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Jianyu Zhan <nasa4836@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Git-commit: 1414c7f4f7d72d138fff35f00151d15749b5beda
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>
Diffstat (limited to 'mm/page_alloc.c')
| -rw-r--r-- | mm/page_alloc.c | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 98d524f3d609..a4cfa64634b4 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1397,15 +1397,24 @@ static inline int check_new_page(struct page *page) return 0; } +static inline bool free_pages_prezeroed(bool poisoned) +{ + return IS_ENABLED(CONFIG_PAGE_POISONING_ZERO) && + page_poisoning_enabled() && poisoned; +} + static int prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags, int alloc_flags) { int i; + bool poisoned = true; for (i = 0; i < (1 << order); i++) { struct page *p = page + i; if (unlikely(check_new_page(p))) return 1; + if (poisoned) + poisoned &= page_is_poisoned(p); } set_page_private(page, 0); @@ -1416,7 +1425,7 @@ static int prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags, kernel_map_pages(page, 1 << order, 1); kernel_poison_pages(page, 1 << order, 1); - if (gfp_flags & __GFP_ZERO) + if (!free_pages_prezeroed(poisoned) && (gfp_flags & __GFP_ZERO)) for (i = 0; i < (1 << order); i++) clear_highpage(page + i); |