net/mlx5: improve stack usage during link update

Allocate no more memory than necessary for the second call to
ETHTOOL_GLINKSETTINGS.

Cc: stable@dpdk.org
Signed-off-by: Nelio Laranjeiro <nelio.laranjeiro@6wind.com>
Acked-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>

diff --git a/drivers/net/mlx5/mlx5_ethdev.c b/drivers/net/mlx5/mlx5_ethdev.c
index 0d2dae4..53a23ab 100644 (file)
--- a/drivers/net/mlx5/mlx5_ethdev.c
+++ b/drivers/net/mlx5/mlx5_ethdev.c
@@ -113,7 +113,6 @@ struct ethtool_link_settings {
 #define ETHTOOL_LINK_MODE_100000baseCR4_Full_BIT 38
 #define ETHTOOL_LINK_MODE_100000baseLR4_ER4_Full_BIT 39
 #endif
-#define ETHTOOL_LINK_MODE_MASK_MAX_KERNEL_NU32 (SCHAR_MAX)
 
 /**
  * Return private structure associated with an Ethernet device.
@@ -805,11 +804,7 @@ static int
 mlx5_link_update_unlocked_gs(struct rte_eth_dev *dev, int wait_to_complete)
 {
        struct priv *priv = mlx5_get_priv(dev);
-       alignas(struct ethtool_link_settings)
-       uint8_t data[offsetof(struct ethtool_link_settings, link_mode_masks) +
-                    sizeof(uint32_t) *
-                    ETHTOOL_LINK_MODE_MASK_MAX_KERNEL_NU32 * 3];
-       struct ethtool_link_settings *ecmd = (void *)data;
+       struct ethtool_link_settings gcmd = { .cmd = ETHTOOL_GLINKSETTINGS };
        struct ifreq ifr;
        struct rte_eth_link dev_link;
        uint64_t sc;
@@ -822,15 +817,21 @@ mlx5_link_update_unlocked_gs(struct rte_eth_dev *dev, int wait_to_complete)
        memset(&dev_link, 0, sizeof(dev_link));
        dev_link.link_status = ((ifr.ifr_flags & IFF_UP) &&
                                (ifr.ifr_flags & IFF_RUNNING));
-       memset(ecmd, 0, sizeof(*ecmd));
-       ecmd->cmd = ETHTOOL_GLINKSETTINGS;
-       ifr.ifr_data = (void *)ecmd;
+       ifr.ifr_data = (void *)&gcmd;
        if (priv_ifreq(priv, SIOCETHTOOL, &ifr)) {
                DEBUG("ioctl(SIOCETHTOOL, ETHTOOL_GLINKSETTINGS) failed: %s",
                      strerror(errno));
                return -1;
        }
-       ecmd->link_mode_masks_nwords = -ecmd->link_mode_masks_nwords;
+       gcmd.link_mode_masks_nwords = -gcmd.link_mode_masks_nwords;
+
+       alignas(struct ethtool_link_settings)
+       uint8_t data[offsetof(struct ethtool_link_settings, link_mode_masks) +
+                    sizeof(uint32_t) * gcmd.link_mode_masks_nwords * 3];
+       struct ethtool_link_settings *ecmd = (void *)data;
+
+       *ecmd = gcmd;
+       ifr.ifr_data = (void *)ecmd;
        if (priv_ifreq(priv, SIOCETHTOOL, &ifr)) {
                DEBUG("ioctl(SIOCETHTOOL, ETHTOOL_GLINKSETTINGS) failed: %s",
                      strerror(errno));