[v3,03/16] fm10k: avoid possible truncation of q_vector->name

Message ID 20170710202319.22110-3-jacob.e.keller@intel.com
State Accepted
Delegated to: Jeff Kirsher
Headers show

Commit Message

Keller, Jacob E July 10, 2017, 8:23 p.m.
New versions of GCC since version 7 began warning about possible
truncation of calls to snprintf. We can fix this and avoid false
positives. First, we should pass the full buffer size to snprintf,
because it guarantees a NULL character as part of its passed length, so
passing len-1 is simply wasting a byte of possible storage.

Second, if we make the ri and ti variables unsigned, the compiler is
able to correctly reason that the value never gets larger than 256, so
it doesn't need to warn about the full space required to print a signed
integer.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
---
 drivers/net/ethernet/intel/fm10k/fm10k_pci.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

Comments

Singh, Krishneil K Sept. 18, 2017, 5:03 p.m. | #1
> -----Original Message-----
> From: Intel-wired-lan [mailto:intel-wired-lan-bounces@osuosl.org] On Behalf
> Of Jacob Keller
> Sent: Monday, July 10, 2017 1:23 PM
> To: jtkirhse@osuosl.org; Intel Wired LAN <intel-wired-lan@lists.osuosl.org>
> Cc: jekeller@osuosl.org
> Subject: [Intel-wired-lan] [PATCH v3 03/16] fm10k: avoid possible truncation of
> q_vector->name
> 
> New versions of GCC since version 7 began warning about possible
> truncation of calls to snprintf. We can fix this and avoid false
> positives. First, we should pass the full buffer size to snprintf,
> because it guarantees a NULL character as part of its passed length, so
> passing len-1 is simply wasting a byte of possible storage.
> 
> Second, if we make the ri and ti variables unsigned, the compiler is
> able to correctly reason that the value never gets larger than 256, so
> it doesn't need to warn about the full space required to print a signed
> integer.
> 
> Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
> ---

Tested-by: Krishneil Singh  <krishneil.k.singh@intel.com>

Patch

diff --git a/drivers/net/ethernet/intel/fm10k/fm10k_pci.c b/drivers/net/ethernet/intel/fm10k/fm10k_pci.c
index 3e26d27ad213..80b18f2479b4 100644
--- a/drivers/net/ethernet/intel/fm10k/fm10k_pci.c
+++ b/drivers/net/ethernet/intel/fm10k/fm10k_pci.c
@@ -1544,7 +1544,7 @@  int fm10k_qv_request_irq(struct fm10k_intfc *interface)
 	struct net_device *dev = interface->netdev;
 	struct fm10k_hw *hw = &interface->hw;
 	struct msix_entry *entry;
-	int ri = 0, ti = 0;
+	unsigned int ri = 0, ti = 0;
 	int vector, err;
 
 	entry = &interface->msix_entries[NON_Q_VECTORS(hw)];
@@ -1554,15 +1554,15 @@  int fm10k_qv_request_irq(struct fm10k_intfc *interface)
 
 		/* name the vector */
 		if (q_vector->tx.count && q_vector->rx.count) {
-			snprintf(q_vector->name, sizeof(q_vector->name) - 1,
-				 "%s-TxRx-%d", dev->name, ri++);
+			snprintf(q_vector->name, sizeof(q_vector->name),
+				 "%s-TxRx-%u", dev->name, ri++);
 			ti++;
 		} else if (q_vector->rx.count) {
-			snprintf(q_vector->name, sizeof(q_vector->name) - 1,
-				 "%s-rx-%d", dev->name, ri++);
+			snprintf(q_vector->name, sizeof(q_vector->name),
+				 "%s-rx-%u", dev->name, ri++);
 		} else if (q_vector->tx.count) {
-			snprintf(q_vector->name, sizeof(q_vector->name) - 1,
-				 "%s-tx-%d", dev->name, ti++);
+			snprintf(q_vector->name, sizeof(q_vector->name),
+				 "%s-tx-%u", dev->name, ti++);
 		} else {
 			/* skip this unused q_vector */
 			continue;