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| author | Jan Beulich <JBeulich@suse.com> | 2016-02-10 12:03:00 +0300 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2016-02-25 12:41:43 +0300 |
| commit | 405e1133d00e0271cedef75c17ecb773ff3e2732 (patch) | |
| tree | 05d6cc18bed901ce2b3355c287695d3a5f92f7b4 /arch/x86/mm/pageattr.c | |
| parent | b176862fca8625b0a8bee207bca9b611413e5e24 (diff) | |
| download | linux-405e1133d00e0271cedef75c17ecb773ff3e2732.tar.xz | |
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 <jbeulich@suse.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/56BB0AD402000078000D05BF@prv-mh.provo.novell.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'arch/x86/mm/pageattr.c')
| -rw-r--r-- | arch/x86/mm/pageattr.c | 4 |
1 files changed, 3 insertions, 1 deletions
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 |