[PATCH] PCI/IOV: Fix out-of-bounds access in sriov_restore_vf_rebar_state()

[Marco Nenciarini <mnencia@kcore.it>]

sriov_restore_vf_rebar_state() extracts bar_idx from the VF Resizable
BAR control register using a 3-bit field (PCI_VF_REBAR_CTRL_BAR_IDX,
bits 0-2), which yields values in the range 0-7. This value is then
used to index into dev->sriov->barsz[], which has PCI_SRIOV_NUM_BARS
(6) entries.

If the PCI config space read returns garbage data (e.g. 0xffffffff when
the device is no longer accessible on the bus), bar_idx is 7, causing
an out-of-bounds array access. UBSAN reports this as:

  UBSAN: array-index-out-of-bounds in drivers/pci/iov.c:948:51
  index 7 is out of range for type 'resource_size_t [6]'

This was observed on an NVIDIA RTX PRO 1000 GPU (GB207GLM) that fell
off the PCIe bus during a failed GC6 power state exit. The subsequent
pci_restore_state() call triggered the UBSAN splat in
sriov_restore_vf_rebar_state() since all config space reads returned
0xffffffff.

Add a bounds check on bar_idx before using it as an array index to
prevent the out-of-bounds access.

Fixes: 5a8f77e24a30 ("PCI/IOV: Restore VF resizable BAR state after reset")
Cc: stable@vger.kernel.org
Signed-off-by: Marco Nenciarini <mnencia@kcore.it>
---
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

 drivers/pci/iov.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index 00784a60b..521f2cb64 100644
--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -946,6 +946,8 @@ static void sriov_restore_vf_rebar_state(struct pci_dev *dev)
 
 		pci_read_config_dword(dev, pos + PCI_VF_REBAR_CTRL, &ctrl);
 		bar_idx = FIELD_GET(PCI_VF_REBAR_CTRL_BAR_IDX, ctrl);
+		if (bar_idx >= PCI_SRIOV_NUM_BARS)
+			continue;
 		size = pci_rebar_bytes_to_size(dev->sriov->barsz[bar_idx]);
 		ctrl &= ~PCI_VF_REBAR_CTRL_BAR_SIZE;
 		ctrl |= FIELD_PREP(PCI_VF_REBAR_CTRL_BAR_SIZE, size);
-- 
2.47.3