From 405e1133d00e0271cedef75c17ecb773ff3e2732 Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Wed, 10 Feb 2016 02:03:00 -0700 Subject: [PATCH] x86/mm: Avoid premature success when changing page attributes set_memory_nx() (and set_memory_x()) currently differ in behavior from all other set_memory_*() functions when encountering a virtual address space hole within the kernel address range: They stop processing at the hole, but nevertheless report success (making the caller believe the operation was carried out on the entire range). While observed to be a problem - triggering the CONFIG_DEBUG_WX warning - only with out of tree code, I suspect (but didn't check) that on x86-64 the CONFIG_DEBUG_PAGEALLOC logic in free_init_pages() would, when called from free_initmem(), have the same effect on the set_memory_nx() called from mark_rodata_ro(). This unexpected behavior is a result of change_page_attr_set_clr() special casing changes to only the NX bit, in that it passes "false" as the "checkalias" argument to __change_page_attr_set_clr(). Since this flag becomes the "primary" argument of both __change_page_attr() and __cpa_process_fault(), the latter would so far return success without adjusting cpa->numpages. Success to the higher level callers, however, means that whatever cpa->numpages currently holds is the count of successfully processed pages. The cases when __change_page_attr() calls __cpa_process_fault(), otoh, don't generally mean the entire range got processed (as can be seen from one of the two success return paths in __cpa_process_fault() already adjusting ->numpages). Signed-off-by: Jan Beulich Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/56BB0AD402000078000D05BF@prv-mh.provo.novell.com Signed-off-by: Thomas Gleixner --- arch/x86/mm/pageattr.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index 2440814b0069..3dd6afd2c0e5 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -1122,8 +1122,10 @@ static int __cpa_process_fault(struct cpa_data *cpa, unsigned long vaddr, /* * Ignore all non primary paths. */ - if (!primary) + if (!primary) { + cpa->numpages = 1; return 0; + } /* * Ignore the NULL PTE for kernel identity mapping, as it is expected -- 2.20.1