powerpc: Fail remap_4k_pfn() if PFN doesn't fit inside PTE

remap_4k_pfn() silently truncates upper bits of input 4K PFN
if it cannot be contained in PTE. This leads invalid memory mapping and could
result in a system crash when the memory is accessed. This patch fails
remap_4k_pfn() and returns -EINVAL if the input 4K PFN cannot be contained in
PTE.

V3 : Added parentheses to protect 'pfn' and entire macro as suggested by Brian.
V2 : Rewritten to avoid helper function as suggested by Stephen Rothwell.

Signed-off-by: Madhusudanan Kandasamy <kmadhu@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/arch/powerpc/include/asm/pte-hash64-64k.h b/arch/powerpc/include/asm/pte-hash64-64k.h
index d836d945068d..b6d2d42f84b5 100644
--- a/arch/powerpc/include/asm/pte-hash64-64k.h
+++ b/arch/powerpc/include/asm/pte-hash64-64k.h
@@ -75,7 +75,8 @@
         (((pte) & _PAGE_COMBO)? MMU_PAGE_4K: MMU_PAGE_64K)
 
 #define remap_4k_pfn(vma, addr, pfn, prot)                              \
-        remap_pfn_range((vma), (addr), (pfn), PAGE_SIZE,                \
-                        __pgprot(pgprot_val((prot)) | _PAGE_4K_PFN))
+        (WARN_ON(((pfn) >= (1UL << (64 - PTE_RPN_SHIFT)))) ? -EINVAL :  \
+                remap_pfn_range((vma), (addr), (pfn), PAGE_SIZE,        \
+                        __pgprot(pgprot_val((prot)) | _PAGE_4K_PFN)))
 
 #endif  /* __ASSEMBLY__ */