[PATCH v2] HID: amd_sfh: Validate PCI BAR size before mapping

[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>
Acked-by: Basavaraj Natikar <Basavaraj.Natikar@amd.com>
---
v2:
* Use SZ_128K for AMD_SFH_MIN_BAR_SIZE define
* Add comment why we need 128K
* Add 'Acked-by: Basavaraj Natikar <Basavaraj.Natikar@amd.com>' since no logical changes

v1:
* https://lore.kernel.org/all/94704655-d654-4500-8122-b80bea9bd908@mail.kernel.org/
---
 drivers/hid/amd-sfh-hid/amd_sfh_common.h |  4 ++++
 drivers/hid/amd-sfh-hid/amd_sfh_pcie.c   | 10 ++++++++++
 2 files changed, 14 insertions(+)

diff --git a/drivers/hid/amd-sfh-hid/amd_sfh_common.h b/drivers/hid/amd-sfh-hid/amd_sfh_common.h
index f8c6b7fc34fb..3d29119a3765 100644
--- a/drivers/hid/amd-sfh-hid/amd_sfh_common.h
+++ b/drivers/hid/amd-sfh-hid/amd_sfh_common.h
@@ -13,11 +13,15 @@
 #include <linux/auxiliary_bus.h>
 #include <linux/mutex.h>
 #include <linux/pci.h>
+#include <linux/sizes.h>
 #include "amd_sfh_hid.h"
 
 #define PCI_DEVICE_ID_AMD_MP2		0x15E4
 #define PCI_DEVICE_ID_AMD_MP2_1_1	0x164A
 
+/* The BAR 2 size must cover the highest register offset (0x10958) */
+#define AMD_SFH_MIN_BAR_SIZE		SZ_128K
+
 #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 eda26a094d3f..061a63519d44 100644
--- a/drivers/hid/amd-sfh-hid/amd_sfh_pcie.c
+++ b/drivers/hid/amd-sfh-hid/amd_sfh_pcie.c
@@ -497,6 +497,16 @@ 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;
-- 
2.55.0