Re: [PATCH] HID: amd_sfh: Validate PCI BAR size before mapping

[Basavaraj Natikar <bnatikar@amd.com>]

On 8/27/2026 12:06 PM, syzbot wrote:
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>
> From: Slawomir Stepien <sst@poczta.fm>
>
> The amd_sfh driver maps PCI BAR 2 using pcim_iomap_regions() and
> subsequently accesses MMIO registers at offsets up to 0x10958 (e.g.,
> AMD_P2C_MSG3 at 0x1068C). However, the driver never validates that the BAR
> size is large enough to cover these accesses. If the driver is bound to a
> device with a smaller BAR 2, this leads to an out-of-bounds memory access
> and a page fault during the probe function.
>
> For example, a page fault can occur when reading from privdata->mmio +
> AMD_P2C_MSG3 in mp2_select_ops():
>
>    BUG: unable to handle page fault for address: ffffc9000390368c
>    PGD 100000067 P4D 100000067 PUD 1012c1067 PMD 105b64067 PTE 0
>    Oops: Oops: 0000 [#1] SMP KASAN NOPTI
>    RIP: 0010:readl arch/x86/include/asm/io.h:59 [inline]
>    RIP: 0010:mp2_select_ops drivers/hid/amd-sfh-hid/amd_sfh_pcie.c:282
>    [inline]
>    RIP: 0010:amd_mp2_pci_probe+0x337/0x5f0
>    drivers/hid/amd-sfh-hid/amd_sfh_pcie.c:487
>    Call Trace:
>     <TASK>
>     local_pci_probe drivers/pci/pci-driver.c:332 [inline]
>     pci_call_probe drivers/pci/pci-driver.c:394 [inline]
>     __pci_device_probe drivers/pci/pci-driver.c:455 [inline]
>     pci_device_probe+0x431/0xc90 drivers/pci/pci-driver.c:489
>
> Fix this by verifying that the length of BAR 2 is at least 128KB before
> attempting to map it. Since the maximum accessed offset is 0x10958, and PCI
> BAR sizes are powers of 2, any legitimate hardware will have a BAR size of
> at least 128KB.
>
> Fixes: 4f567b9f8141 ("SFH: PCIe driver to add support of AMD sensor fusion hub")
> Assisted-by: Gemini:gemini-3.7-flash Gemini:gemini-3.1-pro-preview syzbot
> Reported-by: syzbot+4eadd4dfe9e66522bae8@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=4eadd4dfe9e66522bae8
> Link: https://syzkaller.appspot.com/ai_job?id=3bc1c45c-548f-4ab5-8243-d2c8ec321d6c
> Signed-off-by: Slawomir Stepien <sst@poczta.fm>
>
> ---
> diff --git a/drivers/hid/amd-sfh-hid/amd_sfh_common.h b/drivers/hid/amd-sfh-hid/amd_sfh_common.h
> index 78f830c13..c0c324565 100644
> --- a/drivers/hid/amd-sfh-hid/amd_sfh_common.h
> +++ b/drivers/hid/amd-sfh-hid/amd_sfh_common.h
> @@ -17,6 +17,8 @@
>   #define PCI_DEVICE_ID_AMD_MP2          0x15E4
>   #define PCI_DEVICE_ID_AMD_MP2_1_1      0x164A
>
> +#define AMD_SFH_MIN_BAR_SIZE           (128 * 1024)

Please use SZ_128K instead of the open-coded (128 * 1024), A short comment noting the value
must cover the highest register offset (0x10958) would also help future readers.

With that:
Acked-by: Basavaraj Natikar <Basavaraj.Natikar@amd.com>

Thanks,
--
Basavaraj

> +
>   #define AMD_C2P_MSG(regno) (0x10500 + ((regno) * 4))
>   #define AMD_P2C_MSG(regno) (0x10680 + ((regno) * 4))
>
> diff --git a/drivers/hid/amd-sfh-hid/amd_sfh_pcie.c b/drivers/hid/amd-sfh-hid/amd_sfh_pcie.c
> index 4b81cebdc..039b6ac32 100644
> --- a/drivers/hid/amd-sfh-hid/amd_sfh_pcie.c
> +++ b/drivers/hid/amd-sfh-hid/amd_sfh_pcie.c
> @@ -451,6 +451,16 @@ static int amd_mp2_pci_probe(struct pci_dev *pdev, const struct pci_device_id *i
>          if (rc)
>                  return rc;
>
> +       if (!(pci_resource_flags(pdev, 2) & IORESOURCE_MEM)) {
> +               dev_err(&pdev->dev, "BAR 2 is not IORESOURCE_MEM\n");
> +               return -ENODEV;
> +       }
> +
> +       if (pci_resource_len(pdev, 2) < AMD_SFH_MIN_BAR_SIZE) {
> +               dev_err(&pdev->dev, "BAR 2 is too small\n");
> +               return -EINVAL;
> +       }
> +
>          rc = pcim_iomap_regions(pdev, BIT(2), DRIVER_NAME);
>          if (rc)
>                  return rc;
>
>
> base-commit: db2ddb87143519e20a95aa36c60b36107b736a58
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