net: ti: icssg-prueth: fix use-after-free of CPPI descriptor in RX path

net: ti: icssg-prueth: fix use-after-free of CPPI descriptor in RX path

cppi5_hdesc_get_psdata() returns a pointer into the CPPI descriptor.
In both emac_rx_packet() and emac_rx_packet_zc(), the descriptor is
freed via k3_cppi_desc_pool_free() before the psdata pointer is used
by emac_rx_timestamp(), which dereferences psdata[0] and psdata[1].
This constitutes a use-after-free on every received packet that goes
through the timestamp path.

Defer the descriptor free until after all accesses through the psdata
pointer are complete. For emac_rx_packet(), move the free into the
requeue label so both early-exit and success paths free the descriptor
after all accesses are done. For emac_rx_packet_zc(), move the free to
the end of the loop body after emac_dispatch_skb_zc() (which calls
emac_rx_timestamp()) has returned.

Fixes: 46eeb90f03e0 ("net: ti: icssg-prueth: Use page_pool API for RX buffer allocation")
Signed-off-by: David Carlier <devnexen@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20260320174439.41080-1-devnexen@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>