iwlegacy: Check the return value of pcie_capability_read_*()

On failure pcie_capability_read_dword() sets it's last parameter, 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 without changing the function's behaviour if the
return value of pcie_capability_read_dword is checked to confirm success.

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>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200713175529.29715-3-refactormyself@gmail.com

diff --git a/drivers/net/wireless/intel/iwlegacy/common.c b/drivers/net/wireless/intel/iwlegacy/common.c
index 348c17c..f78e062 100644 (file)
--- a/drivers/net/wireless/intel/iwlegacy/common.c
+++ b/drivers/net/wireless/intel/iwlegacy/common.c
@@ -4286,8 +4286,8 @@ il_apm_init(struct il_priv *il)
         *    power savings, even without L1.
         */
        if (il->cfg->set_l0s) {
-               pcie_capability_read_word(il->pci_dev, PCI_EXP_LNKCTL, &lctl);
-               if (lctl & PCI_EXP_LNKCTL_ASPM_L1) {
+               ret = pcie_capability_read_word(il->pci_dev, PCI_EXP_LNKCTL, &lctl);
+               if (!ret && (lctl & PCI_EXP_LNKCTL_ASPM_L1)) {
                        /* L1-ASPM enabled; disable(!) L0S  */
                        il_set_bit(il, CSR_GIO_REG,
                                   CSR_GIO_REG_VAL_L0S_ENABLED);