[PATCH v4] PCI: mediatek: Fix integer truncation and handle oversized resources

[PATCH v4] PCI: mediatek: Fix integer truncation and handle oversized resources

[Sreeraj S Kurup]

resource_size() returns a resource_size_t, which is 64-bit on 64-bit
architectures or 32-bit systems with LPAE/PAE enabled. Passing this
directly to fls(), which accepts an unsigned int, implicitly
truncates the upper 32 bits.

Furthermore, AHB2PCIE_SIZE() uses a 5-bit mask GENMASK(4, 0). If a
resource size exceeds 2 GiB (order > 31), the log2 size order
overflows the 5-bit mask. Clamping the value silently truncates the
hardware window while leaving the OS resource intact, causing bus
errors when accessing BARs in the unmapped upper region.

Fix this by using fls64(size - 1) to accurately calculate log2 size
orders without off-by-one errors and returning -EINVAL if the resource
size exceeds the maximum supported 31-bit window order.

Signed-off-by: Sreeraj S Kurup <sreekuttan2156239@gmail.com>
---
 drivers/pci/controller/pcie-mediatek.c | 29 ++++++++++++++++++++++++--
 1 file changed, 27 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/pcie-mediatek.c b/drivers/pci/controller/pcie-mediatek.c
index a60d1ae076f8..639884b22ad7 100644
--- a/drivers/pci/controller/pcie-mediatek.c
+++ b/drivers/pci/controller/pcie-mediatek.c
@@ -8,6 +8,7 @@
  */
 
 #include <linux/bitfield.h>
+#include <linux/bitops.h>
 #include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/errno.h>
@@ -686,6 +687,8 @@ static int mtk_pcie_startup_port_v2(struct mtk_pcie_port *port)
 	const struct mtk_pcie_soc *soc = port->pcie->soc;
 	u32 val;
 	int err;
+	resource_size_t size;
+	int size_order;
 
 	entry = resource_list_first_type(&host->windows, IORESOURCE_MEM);
 	if (entry)
@@ -753,8 +756,18 @@ static int mtk_pcie_startup_port_v2(struct mtk_pcie_port *port)
 		mtk_pcie_enable_msi(port);
 
 	/* Set AHB to PCIe translation windows */
+	size = resource_size(mem);
+	if (!size)
+		return -EINVAL;
+
+	size_order = fls64(size - 1);
+	if (size_order > 31) {
+		dev_err(pcie->dev, "Memory resource size too large: %pa\n", &size);
+		return -EINVAL;
+	}
+
 	val = lower_32_bits(mem->start) |
-	      AHB2PCIE_SIZE(fls(resource_size(mem)));
+	      AHB2PCIE_SIZE(size_order);
 	writel(val, port->base + PCIE_AHB_TRANS_BASE0_L);
 
 	val = upper_32_bits(mem->start);
@@ -775,6 +788,8 @@ static int mtk_pcie_startup_port_en7528(struct mtk_pcie_port *port)
 	struct resource_entry *entry;
 	u32 val, link_mask;
 	int err;
+	resource_size_t size;
+	int size_order;
 
 	entry = resource_list_first_type(&host->windows, IORESOURCE_MEM);
 	if (entry)
@@ -829,8 +844,18 @@ static int mtk_pcie_startup_port_en7528(struct mtk_pcie_port *port)
 		mtk_pcie_enable_msi(port);
 
 	/* Set AHB to PCIe translation windows */
+	size = resource_size(mem);
+	if (!size)
+		return -EINVAL;
+
+	size_order = fls64(size - 1);
+	if (size_order > 31) {
+		dev_err(pcie->dev, "Memory resource size too large: %pa\n", &size);
+		return -EINVAL;
+	}
+
 	val = lower_32_bits(mem->start) |
-	      AHB2PCIE_SIZE(fls(resource_size(mem)));
+	      AHB2PCIE_SIZE(size_order);
 	writel(val, port->base + PCIE_AHB_TRANS_BASE0_L);
 
 	val = upper_32_bits(mem->start);
-- 
2.55.0

Re: [PATCH v4] PCI: mediatek: Fix integer truncation and handle oversized resources

[Sreeraj S Kurup]

Hi PCI Maintainers,

Apologies for omitting the revision history in the main patch post.
Here is the complete changelog for v4:

Changelog:
 - v4: Fixed struct device pointer access (pcie->dev) for dev_err().
       Verified build and passed Sashiko review checks.
       [Subject: PCI: mediatek: Fix integer truncation and handle
       oversized resources]

 - v3: Replaced clamping logic with strict size validation
       (size_order > 31 returns -EINVAL), added !size check, and
       updated size calculation to fls64(size - 1) to handle
       power-of-two sizes correctly.
       [Subject: PCI: mediatek: Fix integer truncation and handle
       oversized resources]

 - v2: Added size clamping for size_order > 31 to prevent overflowing
       the 5-bit AHB2PCIE_SIZE() macro mask.
       [Subject: PCI: mediatek: Fix integer truncation in fls() and
       clamp size]

 - v1: Initial submission using fls64() to handle 64-bit resource
       sizes and prevent integer truncation.
       [Subject: PCI: mediatek: Fix integer truncation in fls() for
       resource size]

Best regards,
Sreeraj

Re: [PATCH v4] PCI: mediatek: Fix integer truncation and handle oversized resources

[Manivannan Sadhasivam]

On Wed, Sep 30, 2026 at 12:05:39PM +0000, Sreeraj S Kurup wrote:
> resource_size() returns a resource_size_t, which is 64-bit on 64-bit
> architectures or 32-bit systems with LPAE/PAE enabled. Passing this
> directly to fls(), which accepts an unsigned int, implicitly
> truncates the upper 32 bits.
> 
> Furthermore, AHB2PCIE_SIZE() uses a 5-bit mask GENMASK(4, 0). If a
> resource size exceeds 2 GiB (order > 31), the log2 size order
> overflows the 5-bit mask. Clamping the value silently truncates the
> hardware window while leaving the OS resource intact, causing bus
> errors when accessing BARs in the unmapped upper region.
> 
> Fix this by using fls64(size - 1) to accurately calculate log2 size
> orders without off-by-one errors and returning -EINVAL if the resource
> size exceeds the maximum supported 31-bit window order.
> 
> Signed-off-by: Sreeraj S Kurup <sreekuttan2156239@gmail.com>
> ---
>  drivers/pci/controller/pcie-mediatek.c | 29 ++++++++++++++++++++++++--
>  1 file changed, 27 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/controller/pcie-mediatek.c b/drivers/pci/controller/pcie-mediatek.c
> index a60d1ae076f8..639884b22ad7 100644
> --- a/drivers/pci/controller/pcie-mediatek.c
> +++ b/drivers/pci/controller/pcie-mediatek.c
> @@ -8,6 +8,7 @@
>   */
>  
>  #include <linux/bitfield.h>
> +#include <linux/bitops.h>
>  #include <linux/clk.h>
>  #include <linux/delay.h>
>  #include <linux/errno.h>
> @@ -686,6 +687,8 @@ static int mtk_pcie_startup_port_v2(struct mtk_pcie_port *port)
>  	const struct mtk_pcie_soc *soc = port->pcie->soc;
>  	u32 val;
>  	int err;
> +	resource_size_t size;
> +	int size_order;
>  
>  	entry = resource_list_first_type(&host->windows, IORESOURCE_MEM);
>  	if (entry)
> @@ -753,8 +756,18 @@ static int mtk_pcie_startup_port_v2(struct mtk_pcie_port *port)
>  		mtk_pcie_enable_msi(port);
>  
>  	/* Set AHB to PCIe translation windows */
> +	size = resource_size(mem);
> +	if (!size)
> +		return -EINVAL;

PCI core already rejects the zero sized MEM regions. So this check is a dead
code.

> +
> +	size_order = fls64(size - 1);

This is wrong. AHB2PCIE_SIZE() register needs the full size value to enable the
whole window. Check:

c61df57343bf ("PCI: mediatek: Fix memory mapped IO range size computation")

> +	if (size_order > 31) {
> +		dev_err(pcie->dev, "Memory resource size too large: %pa\n", &size);
> +		return -EINVAL;
> +	}
> +
>  	val = lower_32_bits(mem->start) |
> -	      AHB2PCIE_SIZE(fls(resource_size(mem)));
> +	      AHB2PCIE_SIZE(size_order);

Why can't you just do, fls64(resource_size(mem))?

- Mani

-- 
மணிவண்ணன் சதாசிவம்

Re: [PATCH v4] PCI: mediatek: Fix integer truncation and handle oversized resources

[Sreeraj S Kurup]

Hi Mani,
 
Thanks for the review.
 
I've addressed your comments in v5:
 
- Removed the redundant zero-size check.
- Changed `fls64(size - 1)` to `fls64(size)`.
- Kept the full resource size calculation and added validation to reject oversized windows rather than silently clamping the size order.

 
I'll send the updated patch shortly.
 
Best regards,
Sreeraj

[PATCH v5] PCI: mediatek: Fix integer truncation and handle oversized resources

[Sreeraj S Kurup]

resource_size() returns a resource_size_t, which can be 64-bit on
64-bit architectures or 32-bit systems with LPAE/PAE enabled.
Passing this directly to fls(), which accepts an unsigned int,
implicitly truncates the upper bits.

Furthermore, AHB2PCIE_SIZE() uses a 5-bit mask GENMASK(4, 0). If
the size order exceeds the range representable by this field,
higher bits are discarded by the mask. This can leave the hardware
translation window smaller than the OS resource, causing bus
errors when accessing BARs in the unmapped upper region.

Fix this by using fls64(size) to calculate the size order without
truncating the resource size, and return -EINVAL if the size order
exceeds the supported range.

Changelog:

- v5: Use fls64(size) instead of fls64(size - 1) and remove the
  redundant zero-size check.
- v4: Fix struct device pointer access (pcie->dev) for dev_err().
  Verified build and passed Sashiko review checks.
  [Subject: PCI: mediatek: Fix integer truncation and handle
  oversized resources]
- v3: Replace clamping logic with strict size validation
  (size_order > 31 returns -EINVAL), add a zero-size check,
  and update size calculation to fls64(size - 1).
  [Subject: PCI: mediatek: Fix integer truncation and handle
  oversized resources]
- v2: Add size clamping for size_order > 31 to prevent overflowing
  the 5-bit AHB2PCIE_SIZE() macro mask.
  [Subject: PCI: mediatek: Fix integer truncation in fls()
  and clamp size]
- v1: Initial submission using fls64() to handle 64-bit resource
  sizes and prevent integer truncation.
  [Subject: PCI: mediatek: Fix integer truncation in fls()
  for resource size]

Signed-off-by: Sreeraj S Kurup <sreekuttan2156239@gmail.com>
---
 drivers/pci/controller/pcie-mediatek.c | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/pcie-mediatek.c b/drivers/pci/controller/pcie-mediatek.c
index 3a3e91cd0c21..6821452a82b6 100644
--- a/drivers/pci/controller/pcie-mediatek.c
+++ b/drivers/pci/controller/pcie-mediatek.c
@@ -8,6 +8,7 @@
  */
 
 #include <linux/bitfield.h>
+#include <linux/bitops.h>
 #include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/errno.h>
@@ -686,6 +687,8 @@ static int mtk_pcie_startup_port_v2(struct mtk_pcie_port *port)
 	const struct mtk_pcie_soc *soc = port->pcie->soc;
 	u32 val;
 	int err;
+	resource_size_t size;
+	int size_order;
 
 	entry = resource_list_first_type(&host->windows, IORESOURCE_MEM);
 	if (entry)
@@ -753,8 +756,15 @@ static int mtk_pcie_startup_port_v2(struct mtk_pcie_port *port)
 		mtk_pcie_enable_msi(port);
 
 	/* Set AHB to PCIe translation windows */
+	size = resource_size(mem);
+	size_order = fls64(size);
+	if (size_order > 31) {
+		dev_err(pcie->dev, "Memory resource size too large: %pa\n", &size);
+		return -EINVAL;
+	}
+
 	val = lower_32_bits(mem->start) |
-	      AHB2PCIE_SIZE(fls(resource_size(mem)));
+	      AHB2PCIE_SIZE(size_order);
 	writel(val, port->base + PCIE_AHB_TRANS_BASE0_L);
 
 	val = upper_32_bits(mem->start);
@@ -775,6 +785,8 @@ static int mtk_pcie_startup_port_en7528(struct mtk_pcie_port *port)
 	struct resource_entry *entry;
 	u32 val, link_mask;
 	int err;
+	resource_size_t size;
+	int size_order;
 
 	entry = resource_list_first_type(&host->windows, IORESOURCE_MEM);
 	if (entry)
@@ -829,8 +841,15 @@ static int mtk_pcie_startup_port_en7528(struct mtk_pcie_port *port)
 		mtk_pcie_enable_msi(port);
 
 	/* Set AHB to PCIe translation windows */
+	size = resource_size(mem);
+	size_order = fls64(size);
+	if (size_order > 31) {
+		dev_err(pcie->dev, "Memory resource size too large: %pa\n", &size);
+		return -EINVAL;
+	}
+
 	val = lower_32_bits(mem->start) |
-	      AHB2PCIE_SIZE(fls(resource_size(mem)));
+	      AHB2PCIE_SIZE(size_order);
 	writel(val, port->base + PCIE_AHB_TRANS_BASE0_L);
 
 	val = upper_32_bits(mem->start);
-- 
2.55.0

[PATCH v6] PCI: mediatek: Fix integer truncation and handle oversized resources

[Sreeraj S Kurup]

resource_size() returns a resource_size_t, which can be 64-bit on
64-bit architectures or 32-bit systems with LPAE/PAE enabled.
Passing this directly to fls(), which accepts an unsigned int,
implicitly truncates the upper bits.

Furthermore, AHB2PCIE_SIZE() uses a 5-bit mask GENMASK(4, 0). If
the size order exceeds the range representable by this field,
higher bits are discarded by the mask. This can leave the hardware
translation window smaller than the OS resource, causing bus
errors when accessing BARs in the unmapped upper region.

Fix this by using fls64(size) to calculate the size order without
truncating the resource size, and return -EINVAL if the size order
exceeds the supported range.

Changelog:

- v6: Move oversized resource validation before hardware
  initialization to avoid leaving interrupts unmasked on
  the error path.
- v5: Use fls64(size) instead of fls64(size - 1) and remove the
  redundant zero-size check.
- v4: Fix struct device pointer access (pcie->dev) for dev_err().
  Verified build and passed Sashiko review checks.
  [Subject: PCI: mediatek: Fix integer truncation and handle
  oversized resources]
- v3: Replace clamping logic with strict size validation
  (size_order > 31 returns -EINVAL), add a zero-size check,
  and update size calculation to fls64(size - 1).
  [Subject: PCI: mediatek: Fix integer truncation and handle
  oversized resources]
- v2: Add size clamping for size_order > 31 to prevent overflowing
  the 5-bit AHB2PCIE_SIZE() macro mask.
  [Subject: PCI: mediatek: Fix integer truncation in fls()
  and clamp size]
- v1: Initial submission using fls64() to handle 64-bit resource
  sizes and prevent integer truncation.
  [Subject: PCI: mediatek: Fix integer truncation in fls()
  for resource size]

Signed-off-by: Sreeraj S Kurup <sreekuttan2156239@gmail.com>
---
 drivers/pci/controller/pcie-mediatek.c | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/pcie-mediatek.c b/drivers/pci/controller/pcie-mediatek.c
index 3a3e91cd0c21..cc04a7b862f0 100644
--- a/drivers/pci/controller/pcie-mediatek.c
+++ b/drivers/pci/controller/pcie-mediatek.c
@@ -8,6 +8,7 @@
  */
 
 #include <linux/bitfield.h>
+#include <linux/bitops.h>
 #include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/errno.h>
@@ -686,6 +687,8 @@ static int mtk_pcie_startup_port_v2(struct mtk_pcie_port *port)
 	const struct mtk_pcie_soc *soc = port->pcie->soc;
 	u32 val;
 	int err;
+	resource_size_t size;
+	int size_order;
 
 	entry = resource_list_first_type(&host->windows, IORESOURCE_MEM);
 	if (entry)
@@ -693,6 +696,13 @@ static int mtk_pcie_startup_port_v2(struct mtk_pcie_port *port)
 	if (!mem)
 		return -EINVAL;
 
+	size = resource_size(mem);
+	size_order = fls64(size);
+	if (size_order > 31) {
+		dev_err(pcie->dev, "Memory resource size too large: %pa\n", &size);
+		return -EINVAL;
+	}
+
 	/* MT7622 platforms need to enable LTSSM and ASPM from PCIe subsys */
 	if (pcie->base) {
 		val = readl(pcie->base + PCIE_SYS_CFG_V2);
@@ -754,7 +764,7 @@ static int mtk_pcie_startup_port_v2(struct mtk_pcie_port *port)
 
 	/* Set AHB to PCIe translation windows */
 	val = lower_32_bits(mem->start) |
-	      AHB2PCIE_SIZE(fls(resource_size(mem)));
+	      AHB2PCIE_SIZE(size_order);
 	writel(val, port->base + PCIE_AHB_TRANS_BASE0_L);
 
 	val = upper_32_bits(mem->start);
@@ -775,6 +785,8 @@ static int mtk_pcie_startup_port_en7528(struct mtk_pcie_port *port)
 	struct resource_entry *entry;
 	u32 val, link_mask;
 	int err;
+	resource_size_t size;
+	int size_order;
 
 	entry = resource_list_first_type(&host->windows, IORESOURCE_MEM);
 	if (entry)
@@ -782,6 +794,13 @@ static int mtk_pcie_startup_port_en7528(struct mtk_pcie_port *port)
 	if (!mem)
 		return -EINVAL;
 
+	size = resource_size(mem);
+	size_order = fls64(size);
+	if (size_order > 31) {
+		dev_err(pcie->dev, "Memory resource size too large: %pa\n", &size);
+		return -EINVAL;
+	}
+
 	if (!pcie->cfg) {
 		dev_err(pcie->dev, "EN7528: pciecfg syscon not available\n");
 		return -EINVAL;
@@ -830,7 +849,7 @@ static int mtk_pcie_startup_port_en7528(struct mtk_pcie_port *port)
 
 	/* Set AHB to PCIe translation windows */
 	val = lower_32_bits(mem->start) |
-	      AHB2PCIE_SIZE(fls(resource_size(mem)));
+	      AHB2PCIE_SIZE(size_order);
 	writel(val, port->base + PCIE_AHB_TRANS_BASE0_L);
 
 	val = upper_32_bits(mem->start);
-- 
2.55.0