Currently, pci_mmap_legacy_page_range() reads the legacy resource
size from bus->legacy_mem->size or bus->legacy_io->size.  This
couples the mmap bounds check to the struct pci_bus fields that
will be removed when legacy attributes are converted to static
definitions.

Compute the size directly using PCI_LEGACY_MEM_SIZE (0x100000) and
PCI_LEGACY_IO_SIZE (0xffff) macros, and shift by 5 bits for sparse
systems.

Tested-by: Magnus Lindholm <linmag7@gmail.com>
Tested-by: Shivaprasad G Bhat <redacted>
Acked-by: Magnus Lindholm <linmag7@gmail.com>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
---
 arch/alpha/kernel/pci-sysfs.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/alpha/kernel/pci-sysfs.c b/arch/alpha/kernel/pci-sysfs.c
index ae448a2e40c5..74c9145e0253 100644
--- a/arch/alpha/kernel/pci-sysfs.c
+++ b/arch/alpha/kernel/pci-sysfs.c

@@ -173,8 +173,11 @@ int pci_mmap_legacy_page_range(struct pci_bus *bus, struct vm_area_struct *vma,
 	int sparse = has_sparse(hose, mmap_type);
 	unsigned long res_size;
 
-	res_size = (mmap_type == pci_mmap_mem) ? bus->legacy_mem->size :
-						 bus->legacy_io->size;
+	res_size = (mmap_type == pci_mmap_mem) ? PCI_LEGACY_MEM_SIZE :
+						 PCI_LEGACY_IO_SIZE;
+	if (sparse)
+		res_size <<= 5;
+
 	if (!__legacy_mmap_fits(vma, res_size))
 		return -EINVAL;
 

-- 
2.54.0