ata: ahci: fail probe if BAR too small for claimed ports

When an AHCI controller is disabled in BIOS, its HOST_CAP register may
contain a bogus value, e.g. 0xFFFFFFFF.

Since CAP.NP (Number of Ports) is a zeroes based 5-bit register field,
a value of 0x1f means 32 ports. If CAP.NP claims more ports than can
physically fit within the mapped BAR region, accessing port registers
beyond the BAR boundary causes a kernel panic.

Add validation in ahci_init_one() to check that the BAR size is
sufficient for the number of ports claimed in CAP.NP. The check
calculates the required MMIO size as:

  required_size = 0x100 (global registers) + max_ports * 0x80

If required_size exceeds the actual BAR size, the probe fails with
-ENODEV, preventing the panic and providing a clear error message.

Reported-by: liyouhong <liyouhong@kylinos.cn>
Closes: https://lore.kernel.org/all/20260422080322.1006592-1-dayou5941@163.com/
Suggested-by: Damien Le Moal <dlemoal@kernel.org>
Suggested-by: Niklas Cassel <cassel@kernel.org>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: liyouhong <liyouhong@kylinos.cn>
[cassel: commit log]
Signed-off-by: Niklas Cassel <cassel@kernel.org>

diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index 1d73a53370cf3ea79229850dd8243c7afc6800d2..b4e5d347151a9085cefa09e7c30b30e124e44cd1 100644 (file)
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -1888,6 +1888,24 @@ static ssize_t remapped_nvme_show(struct device *dev,
 
 static DEVICE_ATTR_RO(remapped_nvme);
 
+static int ahci_validate_bar_size(struct pci_dev *pdev, int bar,
+                                 struct ahci_host_priv *hpriv)
+{
+       u32 cap = readl(hpriv->mmio + HOST_CAP);
+       unsigned int max_ports = ahci_nr_ports(cap);
+       u32 last_port_end = 0x100 + (max_ports * 0x80);
+       resource_size_t bar_size = pci_resource_len(pdev, bar);
+
+       if (last_port_end > bar_size) {
+               dev_warn(&pdev->dev,
+                        "BAR%d too small for %u ports (last port ends at %#x, BAR %pa)\n",
+                        bar, max_ports, last_port_end, &bar_size);
+               return -ENODEV;
+       }
+
+       return 0;
+}
+
 static int ahci_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 {
        unsigned int board_id = ent->driver_data;
@@ -1988,6 +2006,10 @@ static int ahci_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
        if (!hpriv->mmio)
                return -ENOMEM;
 
+       rc = ahci_validate_bar_size(pdev, ahci_pci_bar, hpriv);
+       if (rc)
+               return rc;
+
        /* detect remapped nvme devices */
        ahci_remap_check(pdev, ahci_pci_bar, hpriv);