riscv: Fix is_linear_mapping with recent move of KASAN region

The KASAN region was recently moved between the linear mapping and the
kernel mapping, is_linear_mapping used to check the validity of an
address by using the start of the kernel mapping, which is now wrong.

Fix this by using the maximum size of the physical memory.

Fixes: f7ae02333d ("riscv: Move KASAN mapping next to the kernel mapping")
Signed-off-by: Alexandre Ghiti <alexandre.ghiti@canonical.com>
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/include/asm/page.h

@@ -119,7 +119,7 @@ extern phys_addr_t phys_ram_base;
 	((x) >= kernel_map.virt_addr && (x) < (kernel_map.virt_addr + kernel_map.size))
 
 #define is_linear_mapping(x)	\
-	((x) >= PAGE_OFFSET && (!IS_ENABLED(CONFIG_64BIT) || (x) < kernel_map.virt_addr))
+	((x) >= PAGE_OFFSET && (!IS_ENABLED(CONFIG_64BIT) || (x) < PAGE_OFFSET + KERN_VIRT_SIZE))
 
 #define linear_mapping_pa_to_va(x)	((void *)((unsigned long)(x) + kernel_map.va_pa_offset))
 #define kernel_mapping_pa_to_va(y)	({						\

arch/riscv/include/asm/pgtable.h

@@ -13,6 +13,7 @@
 
 #ifndef CONFIG_MMU
 #define KERNEL_LINK_ADDR	PAGE_OFFSET
+#define KERN_VIRT_SIZE		(UL(-1))
 #else
 
 #define ADDRESS_SPACE_END	(UL(-1))