[PATCH 11/14 v4] PCI/PM: Check return value of pcie_capability_read_*()

Saheed Olayemi Bolarinwa
2020-07-14T10:04:44Z

val to 0.
However, with Patch 14/14, it is possible that val is set to ~0 on
failure. This would introduce a bug because (x & x) == (~0 & x).

This bug can be avoided if the return value of pcie_capability_read_dword
is checked to confirm success/failure. This check helps ensure that
functions exit only when their post-condition is true. For functions which
walks through device heirarchy like pci_enable_atomic_ops_to_root(), this
is important.

Check the return value of pcie_capability_read_dword() to ensure success.

Suggested-by: Bjorn Helgaas <bjorn@helgaas.com>
Signed-off-by: Bolarinwa Olayemi Saheed <refactormyself@gmail.com>
---
v4 changes:
Remove unnecessary boolean conversion.
Fix bugs introduced by previous changes

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 4b2a348576cb..d82b79291742 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -3207,6 +3207,7 @@ void pci_configure_ari(struct pci_dev *dev)
{
u32 cap;
struct pci_dev *bridge;
+ int ret;

if (pcie_ari_disabled || !pci_is_pcie(dev) || dev->devfn)
return;
@@ -3215,8 +3216,8 @@ void pci_configure_ari(struct pci_dev *dev)
if (!bridge)
return;

- pcie_capability_read_dword(bridge, PCI_EXP_DEVCAP2, &cap);
- if (!(cap & PCI_EXP_DEVCAP2_ARI))
+ ret = pcie_capability_read_dword(bridge, PCI_EXP_DEVCAP2, &cap);
+ if (ret || !(cap & PCI_EXP_DEVCAP2_ARI))
return;

if (pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ARI)) {
@@ -3606,6 +3607,7 @@ int pci_enable_atomic_ops_to_root(struct pci_dev *dev, u32 cap_mask)
struct pci_bus *bus = dev->bus;
struct pci_dev *bridge;
u32 cap, ctl2;
+ int ret;

if (!pci_is_pcie(dev))
return -EINVAL;
@@ -3629,28 +3631,29 @@ int pci_enable_atomic_ops_to_root(struct pci_dev *dev, u32 cap_mask)
while (bus->parent) {
bridge = bus->self;

- pcie_capability_read_dword(bridge, PCI_EXP_DEVCAP2, &cap);
+ ret = pcie_capability_read_dword(bridge, PCI_EXP_DEVCAP2,
+ &cap);

switch (pci_pcie_type(bridge)) {
/* Ensure switch ports support AtomicOp routing */
case PCI_EXP_TYPE_UPSTREAM:
case PCI_EXP_TYPE_DOWNSTREAM:
- if (!(cap & PCI_EXP_DEVCAP2_ATOMIC_ROUTE))
+ if (ret || !(cap & PCI_EXP_DEVCAP2_ATOMIC_ROUTE))
return -EINVAL;
break;

/* Ensure root port supports all the sizes we care about */
case PCI_EXP_TYPE_ROOT_PORT:
- if ((cap & cap_mask) != cap_mask)
+ if (ret || ((cap & cap_mask) != cap_mask))
return -EINVAL;
break;
}

/* Ensure upstream ports don't block AtomicOps on egress */
if (pci_pcie_type(bridge) == PCI_EXP_TYPE_UPSTREAM) {
- pcie_capability_read_dword(bridge, PCI_EXP_DEVCTL2,
- &ctl2);
- if (ctl2 & PCI_EXP_DEVCTL2_ATOMIC_EGRESS_BLOCK)
+ ret = pcie_capability_read_dword(bridge,
+ PCI_EXP_DEVCTL2, &ctl2);
+ if (!ret && (ctl2 & PCI_EXP_DEVCTL2_ATOMIC_EGRESS_BLOCK)
return -EINVAL;
}

@@ -4507,12 +4510,13 @@ EXPORT_SYMBOL(pci_wait_for_pending_transaction);
bool pcie_has_flr(struct pci_dev *dev)
{
u32 cap;
+ int ret;

if (dev->dev_flags & PCI_DEV_FLAGS_NO_FLR_RESET)
return false;

- pcie_capability_read_dword(dev, PCI_EXP_DEVCAP, &cap);
- return cap & PCI_EXP_DEVCAP_FLR;
+ ret = pcie_capability_read_dword(dev, PCI_EXP_DEVCAP, &cap);
+ return (!ret && (cap & PCI_EXP_DEVCAP_FLR));
}
EXPORT_SYMBOL_GPL(pcie_has_flr);

@@ -4646,7 +4650,7 @@ static int pci_pm_reset(struct pci_dev *dev, int probe)
static bool pcie_wait_for_link_delay(struct pci_dev *pdev, bool active,
int delay)
{
- int timeout = 1000;
+ int rc, timeout = 1000;
bool ret;
u16 lnk_status;

@@ -4671,9 +4675,9 @@ static bool pcie_wait_for_link_delay(struct pci_dev *pdev, bool active,
if (active)
msleep(20);
for (;;) {
- pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnk_status);
- ret = !!(lnk_status & PCI_EXP_LNKSTA_DLLLA);
- if (ret == active)
+ rc = pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnk_status);
+ ret = !!(lnk_status & PCI_EXP_LNKSTA_DLLLA);
+ if (!rc && (ret == active))
break;
if (timeout <= 0)
break;
@@ -4682,10 +4686,10 @@ static bool pcie_wait_for_link_delay(struct pci_dev *pdev, bool active,
}
if (active && ret && delay)
msleep(delay);
- else if (ret != active)
+ else if (rc || (ret != active))
pci_info(pdev, "Data Link Layer Link Active not %s in 1000 msec\n",
active ? "set" : "cleared");
- return ret == active;
+ return (!rc && (ret == active));
}

/**
@@ -5774,6 +5778,7 @@ u32 pcie_bandwidth_available(struct pci_dev *dev, struct pci_dev **limiting_dev,
enum pci_bus_speed next_speed;
enum pcie_link_width next_width;
u32 bw, next_bw;
+ int ret;

if (speed)
*speed = PCI_SPEED_UNKNOWN;
@@ -5783,7 +5788,12 @@ u32 pcie_bandwidth_available(struct pci_dev *dev, struct pci_dev **limiting_dev,
bw = 0;

while (dev) {
- pcie_capability_read_word(dev, PCI_EXP_LNKSTA, &lnksta);
+ ret = pcie_capability_read_word(dev, PCI_EXP_LNKSTA, &lnksta);
+
+ if (ret) {
+ dev = pci_upstream_bridge(dev);
+ continue;
+ }

next_speed = pcie_link_speed[lnksta & PCI_EXP_LNKSTA_CLS];
next_width = (lnksta & PCI_EXP_LNKSTA_NLW) >>
@@ -5820,6 +5830,7 @@ EXPORT_SYMBOL(pcie_bandwidth_available);
enum pci_bus_speed pcie_get_speed_cap(struct pci_dev *dev)
{
u32 lnkcap2, lnkcap;
+ int ret;

/*
* Link Capabilities 2 was added in PCIe r3.0, sec 7.8.18. The
@@ -5830,16 +5841,18 @@ enum pci_bus_speed pcie_get_speed_cap(struct pci_dev *dev)
* should use the Supported Link Speeds field in Link Capabilities,
* where only 2.5 GT/s and 5.0 GT/s speeds were defined.
*/
- pcie_capability_read_dword(dev, PCI_EXP_LNKCAP2, &lnkcap2);
+ ret = pcie_capability_read_dword(dev, PCI_EXP_LNKCAP2, &lnkcap2);

/* PCIe r3.0-compliant */
- if (lnkcap2)
+ if (!ret && lnkcap2)
return PCIE_LNKCAP2_SLS2SPEED(lnkcap2);

- pcie_capability_read_dword(dev, PCI_EXP_LNKCAP, &lnkcap);
- if ((lnkcap & PCI_EXP_LNKCAP_SLS) == PCI_EXP_LNKCAP_SLS_5_0GB)
+ ret = pcie_capability_read_dword(dev, PCI_EXP_LNKCAP, &lnkcap);
+ if (!ret &&
+ ((lnkcap & PCI_EXP_LNKCAP_SLS) == PCI_EXP_LNKCAP_SLS_5_0GB))
return PCIE_SPEED_5_0GT;
- else if ((lnkcap & PCI_EXP_LNKCAP_SLS) == PCI_EXP_LNKCAP_SLS_2_5GB)
+ else if (!ret &&
+ ((lnkcap & PCI_EXP_LNKCAP_SLS) == PCI_EXP_LNKCAP_SLS_2_5GB))
return PCIE_SPEED_2_5GT;

return PCI_SPEED_UNKNOWN;
@@ -5856,9 +5869,10 @@ EXPORT_SYMBOL(pcie_get_speed_cap);
enum pcie_link_width pcie_get_width_cap(struct pci_dev *dev)
{
u32 lnkcap;
+ int ret;

- pcie_capability_read_dword(dev, PCI_EXP_LNKCAP, &lnkcap);
- if (lnkcap)
+ ret = pcie_capability_read_dword(dev, PCI_EXP_LNKCAP, &lnkcap);
+ if (!ret && lnkcap)
return (lnkcap & PCI_EXP_LNKCAP_MLW) >> 4;

return PCIE_LNK_WIDTH_UNKNOWN;