x86: check physical address range in ioremap

Roland Dreier reported in http://lkml.org/lkml/2008/2/27/194

[ 8425.915139] BUG: unable to handle kernel paging request at ffffc20001a0a000
[ 8425.919087] IP: [<ffffffff8021dacc>] clflush_cache_range+0xc/0x25
[ 8425.919087] PGD 1bf80e067 PUD 1bf80f067 PMD 1bb497067 PTE 80000047000ee17b

This is on a Intel machine with 36bit physical address space. The PTE
entry references 47000ee000, which is outside of it.

Add a check for the physical address space and warn/printk about the
stupid caller.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/mm/ioremap.c

@@ -35,6 +35,18 @@ unsigned long __phys_addr(unsigned long x)
 }
 EXPORT_SYMBOL(__phys_addr);
 
+static inline int phys_addr_valid(unsigned long addr)
+{
+	return addr < (1UL << boot_cpu_data.x86_phys_bits);
+}
+
+#else
+
+static inline int phys_addr_valid(unsigned long addr)
+{
+	return 1;
+}
+
 #endif
 
 int page_is_ram(unsigned long pagenr)
@@ -118,6 +130,13 @@ static void __iomem *__ioremap(resource_size_t phys_addr, unsigned long size,
 	if (!size || last_addr < phys_addr)
 		return NULL;
 
+	if (!phys_addr_valid(phys_addr)) {
+		printk(KERN_WARNING "ioremap: invalid physical address %lx\n",
+		       phys_addr);
+		WARN_ON_ONCE(1);
+		return NULL;
+	}
+
 	/*
 	 * Don't remap the low PCI/ISA area, it's always mapped..
 	 */