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>

0 files changed, 0 insertions, 0 deletions