net: stmmac: ptp: limit n_per_out

ptp_clock_ops.n_per_out sets the number of PPS outputs, which the PTP
subsystem uses to validate userspace input, such as the index number
used in a PTP_CLK_REQ_PEROUT request.

stmmac_enable() uses this to index the priv->pps array, which is an
array of size STMMAC_PPS_MAX. ptp_clock_ops.n_per_out is initialised
using priv->dma_cap.pps_out_num, which is a three bit field read from
hardware.

Documentation that I've checked suggests that values >= 5 are reserved,
but that doesn't mean such values won't appear, and if they do, we
can overrun the priv->pps array in stmmac_enable().

stmmac_ptp_register() has protection against this in its loop, but it
doesn't act to limit ptp_clock_ops.n_per_out.

Fix this by introducing a local variable, pps_out_num which is limited
to STMMAC_PPS_MAX, and use that when initialising the array and setting
priv->ptp_clock_ops.n_per_out. Print a warning when we limit the number
of outputs.

Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://patch.msgid.link/E1vvBhn-0000000ArCg-4C4u@rmk-PC.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c
index 3e30172fa129483bf79940ca180785dcfe2a1f07..98da499ba3b15c5fd36a9b58a70ac388d1defa75 100644 (file)
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c
@@ -334,14 +334,19 @@ const struct ptp_clock_info dwmac1000_ptp_clock_ops = {
  */
 void stmmac_ptp_register(struct stmmac_priv *priv)
 {
+       unsigned int pps_out_num = priv->dma_cap.pps_out_num;
        int i;
 
-       for (i = 0; i < priv->dma_cap.pps_out_num; i++) {
-               if (i >= STMMAC_PPS_MAX)
-                       break;
-               priv->pps[i].available = true;
+       if (pps_out_num > STMMAC_PPS_MAX) {
+               dev_warn(priv->device,
+                        "pps outputs (%u) exceeds driver maximum, limiting to %u\n",
+                        pps_out_num, STMMAC_PPS_MAX);
+               pps_out_num = STMMAC_PPS_MAX;
        }
 
+       for (i = 0; i < pps_out_num; i++)
+               priv->pps[i].available = true;
+
        /* Calculate the clock domain crossing (CDC) error if necessary */
        priv->plat->cdc_error_adj = 0;
        if (priv->plat->core_type == DWMAC_CORE_GMAC4)
@@ -350,8 +355,8 @@ void stmmac_ptp_register(struct stmmac_priv *priv)
        /* Update the ptp clock parameters based on feature discovery, when
         * available
         */
-       if (priv->dma_cap.pps_out_num)
-               priv->ptp_clock_ops.n_per_out = priv->dma_cap.pps_out_num;
+       if (pps_out_num)
+               priv->ptp_clock_ops.n_per_out = pps_out_num;
 
        if (priv->dma_cap.aux_snapshot_n)
                priv->ptp_clock_ops.n_ext_ts = priv->dma_cap.aux_snapshot_n;