linux-kernel - [PATCH 4/14 v3] iwlegacy: Check the return value of pcie_capability_read

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Message-Id: <20200713175529.29715-3-refactormyself@gmail.com>
Date:   Mon, 13 Jul 2020 19:55:27 +0200
From:   "Saheed O. Bolarinwa" <refactormyself@...il.com>
To:     skhan@...uxfoundation.org, linux-pci@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        linux-kernel@...r.kernel.org, Stanislaw Gruszka <stf_xl@...pl>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Cc:     Bolarinwa Olayemi Saheed <refactormyself@...il.com>,
        Kalle Valo <kvalo@...eaurora.org>
Subject: [PATCH 4/14 v3] iwlegacy: Check the return value of pcie_capability_read_*()

From: Bolarinwa Olayemi Saheed <refactormyself@...il.com>

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@...gaas.com>
Signed-off-by: Bolarinwa Olayemi Saheed <refactormyself@...il.com>

---
 drivers/net/wireless/intel/iwlegacy/common.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/intel/iwlegacy/common.c b/drivers/net/wireless/intel/iwlegacy/common.c
index 348c17ce72f5..f78e062df572 100644
--- 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);
-- 
2.18.2