[PATCH v5 14/23] alpha/PCI: Fix __pci_mmap_fits() overflow for zero-length BARs

Krzysztof Wilczyński
2026-04-16T18:02:01Z

Currently, __pci_mmap_fits() computes the BAR size using
pci_resource_len() - 1, which wraps to a large value when the
BAR length is zero, causing the bounds check to incorrectly
succeed.

Thus, add an early return for empty resources.

Fixes: 10a0ef39fbd1 ("PCI/alpha: pci sysfs resources")
Tested-by: Magnus Lindholm <linmag7@gmail.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Acked-by: Magnus Lindholm <linmag7@gmail.com>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
---
arch/alpha/kernel/pci-sysfs.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/alpha/kernel/pci-sysfs.c b/arch/alpha/kernel/pci-sysfs.c
index 5c29f1d2821c..8802f955256e 100644
--- a/arch/alpha/kernel/pci-sysfs.c
+++ b/arch/alpha/kernel/pci-sysfs.c
@@ -37,12 +37,16 @@ static int hose_mmap_page_range(struct pci_controller *hose,
static int __pci_mmap_fits(struct pci_dev *pdev, int num,
struct vm_area_struct *vma, int sparse)
{
+ resource_size_t len = pci_resource_len(pdev, num);
unsigned long nr, start, size;
int shift = sparse ? 5 : 0;

+ if (!len)
+ return 0;
+
nr = vma_pages(vma);
start = vma->vm_pgoff;
- size = ((pci_resource_len(pdev, num) - 1) >> (PAGE_SHIFT - shift)) + 1;
+ size = ((len - 1) >> (PAGE_SHIFT - shift)) + 1;

if (start < size && size - start >= nr)
return 1;
--
2.53.0