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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>