[PATCH] x86, PAT: honor CONFIG_STRICT_DEVMEM if pat is disable

[Michal Hocko]

since 0124cecf (x86, PAT: disable /dev/mem mmap RAM with PAT) we are
disabling access to the system RAM as if STRICT_DEVMEM was enabled by
default. If we, however, disable pat by nopat kernel parameter we can
access that memory without considering CONFIG_STRICT_DEVMEM.

Let's make the code to honor STRICT_DEVMEM while we still preserve
disabled by default behavior. This means that the access to the system
memory is granted only if nopat is provided and STRICT_DEVMEM is
disabled.

Signed-off-by: Michal Hocko <mhocko@xxxxxxx>
---
 arch/x86/mm/pat.c |   10 ++--------
 1 files changed, 2 insertions(+), 8 deletions(-)

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index f6ff57b..fbaf3fc 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -472,13 +472,6 @@ pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 	return vma_prot;
 }
 
-#ifdef CONFIG_STRICT_DEVMEM
-/* This check is done in drivers/char/mem.c in case of STRICT_DEVMEM*/
-static inline int range_is_allowed(unsigned long pfn, unsigned long size)
-{
-	return 1;
-}
-#else
 /* This check is needed to avoid cache aliasing when PAT is enabled */
 static inline int range_is_allowed(unsigned long pfn, unsigned long size)
 {
@@ -486,8 +479,10 @@ static inline int range_is_allowed(unsigned long pfn, unsigned long size)
 	u64 to = from + size;
 	u64 cursor = from;
 
+#ifndef CONFIG_STRICT_DEVMEM
 	if (!pat_enabled)
 		return 1;
+#endif
 
 	while (cursor < to) {
 		if (!devmem_is_allowed(pfn)) {
@@ -501,7 +496,6 @@ static inline int range_is_allowed(unsigned long pfn, unsigned long size)
 	}
 	return 1;
 }
-#endif /* CONFIG_STRICT_DEVMEM */
 
 int phys_mem_access_prot_allowed(struct file *file, unsigned long pfn,
 				unsigned long size, pgprot_t *vma_prot)
-- 
1.7.5.4

-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic
--
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