[PATCH] PCI: probe: Fix 64-bit limit truncation in prefetchable window

[PATCH] PCI: probe: Fix 64-bit limit truncation in prefetchable window

[Mohamad Raizudeen]

In pci_read_bridge_mmio_pref(), the code checks if the 64 bit base
address is truncated on 32 bit pci_bus_addr_t. However, it misses this
same check for the limit address.

If firmware sets a window that starts below 4GB but ends above 4GB, the
base check passes. But the 64 bit limit is silently cut down to 32 bits
and wraps around to zero. This makes the base larger than the limit,
causing the kernel to silently disable the memory window instead of
printing an error.

Fix this by checking if the limit was truncated, just like the base.
Also, update the error message to print both the base and limit
addresses to make debugging easier.

Fixes: 7fc986d8a9727 ("PCI: Support 64-bit bridge windows if we have 64-bit dma_addr_t")
Signed-off-by: Mohamad Raizudeen <raizudeen.kerneldev@gmail.com>
---
 drivers/pci/probe.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index dd0abbc63e18..0cf2d1d35146 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -479,9 +479,10 @@ static void pci_read_bridge_mmio_pref(struct pci_dev *dev, struct resource *res,
 	base = (pci_bus_addr_t) base64;
 	limit = (pci_bus_addr_t) limit64;
 
-	if (base != base64) {
-		pci_err(dev, "can't handle bridge window above 4GB (bus address %#010llx)\n",
-			(unsigned long long) base64);
+	if (base != base64 || limit != limit64) {
+		pci_err(dev, "can't handle bridge window above 4GB (bus address %#010llx-%#010llx)\n",
+			(unsigned long long) base64,
+			(unsigned long long) limit64);
 		return;
 	}
 
-- 
2.53.0

Re: [PATCH] PCI: probe: Fix 64-bit limit truncation in prefetchable window

[Mohamad Raizudeen]

On Fri, Aug 14, 2026 at 10:16:52PM +0530, Mohamad Raizudeen wrote:
> In pci_read_bridge_mmio_pref(), the code checks if the 64 bit base
> address is truncated on 32 bit pci_bus_addr_t. However, it misses this
> same check for the limit address.
> 
> If firmware sets a window that starts below 4GB but ends above 4GB, the
> base check passes. But the 64 bit limit is silently cut down to 32 bits
> and wraps around to zero. This makes the base larger than the limit,
> causing the kernel to silently disable the memory window instead of
> printing an error.
> 
> Fix this by checking if the limit was truncated, just like the base.
> Also, update the error message to print both the base and limit
> addresses to make debugging easier.
> 
> Fixes: 7fc986d8a9727 ("PCI: Support 64-bit bridge windows if we have 64-bit dma_addr_t")
> Signed-off-by: Mohamad Raizudeen <raizudeen.kerneldev@gmail.com>
> ---
>  drivers/pci/probe.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index dd0abbc63e18..0cf2d1d35146 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -479,9 +479,10 @@ static void pci_read_bridge_mmio_pref(struct pci_dev *dev, struct resource *res,
>  	base = (pci_bus_addr_t) base64;
>  	limit = (pci_bus_addr_t) limit64;
>  
> -	if (base != base64) {
> -		pci_err(dev, "can't handle bridge window above 4GB (bus address %#010llx)\n",
> -			(unsigned long long) base64);
> +	if (base != base64 || limit != limit64) {
> +		pci_err(dev, "can't handle bridge window above 4GB (bus address %#010llx-%#010llx)\n",
> +			(unsigned long long) base64,
> +			(unsigned long long) limit64);
>  		return;
>  	}
>  
> -- 
> 2.53.0
>
Hi Bjorn,

Just following up on this patch. Please let me know if you have any
feedback or if further changes are needed.

Thanks,
Mohamad Raizudeen