x86: Fix improper large page preservation
This patch fixes a bug in try_preserve_large_page() which may result in improper large page preservation and improper application of page attributes to the memory area outside of the original change request. More specifically, the problem manifests itself when set_memory_*() is called for several pages at the beginning of the large page and try_preserve_large_page() erroneously concludes that the change can be applied to whole large page. The fix consists of 3 parts: 1. Addition of "required" protection attributes in static_protections(), so .data and .bss can be guaranteed to stay "RW" 2. static_protections() is now called for every small page within large page to determine compatibility of new protection attributes (instead of just small pages within the requested range). 3. Large page can be preserved only if attribute change is large-page-aligned and covers whole large page. -v1: Try_preserve_large_page() patch for Linux 2.6.34-rc2 -v2: Replaced pfn check with address check for kernel rw-data Signed-off-by: NSiarhei Liakh <sliakh.lkml@gmail.com> Signed-off-by: NXuxian Jiang <jiang@cs.ncsu.edu> Reviewed-by: NSuresh Siddha <suresh.b.siddha@intel.com> Cc: Arjan van de Ven <arjan@infradead.org> Cc: James Morris <jmorris@namei.org> Cc: Andi Kleen <ak@muc.de> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Dave Jones <davej@redhat.com> Cc: Kees Cook <kees.cook@canonical.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> LKML-Reference: <4CE2F7F3.8030809@free.fr> Signed-off-by: NIngo Molnar <mingo@elte.hu>
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