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

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-3.6-flash Gemini:gemini-3.1-pro-preview syzbot
Reported-by: [email protected]
Closes: https://syzkaller.appspot.com/bug?extid=4eadd4dfe9e66522bae8
Link: https://syzkaller.appspot.com/ai_job?id=7a94b74c-2359-4cbe-b08b-2c52f3bf9755
To: "Basavaraj Natikar" <[email protected]>
To: "Benjamin Tissoires" <[email protected]>
To: "Jiri Kosina" <[email protected]>
To: <[email protected]>
To: "Sandeep Singh" <[email protected]>
Cc: <[email protected]>

---
diff --git a/drivers/hid/amd-sfh-hid/amd_sfh_pcie.c b/drivers/hid/amd-sfh-hid/amd_sfh_pcie.c
index 4b81cebdc..c1dbee87c 100644
--- a/drivers/hid/amd-sfh-hid/amd_sfh_pcie.c
+++ b/drivers/hid/amd-sfh-hid/amd_sfh_pcie.c
@@ -451,6 +451,11 @@ static int amd_mp2_pci_probe(struct pci_dev *pdev, const struct pci_device_id *i
 	if (rc)
 		return rc;
 
+	if (pci_resource_len(pdev, 2) < 128 * 1024) {
+		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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