octeon_ep_vf: add NULL check for napi_build_skb()

octeon_ep_vf: add NULL check for napi_build_skb()

[ Upstream commit dd66b42854705e4e4ee7f14d260f86c578bed3e3 ]

napi_build_skb() can return NULL on allocation failure. In
__octep_vf_oq_process_rx(), the result is used directly without a NULL
check in both the single-buffer and multi-fragment paths, leading to a
NULL pointer dereference.

Add NULL checks after both napi_build_skb() calls, properly advancing
descriptors and consuming remaining fragments on failure.

Fixes: 1cd3b407977c ("octeon_ep_vf: add Tx/Rx processing and interrupt support")
Cc: stable@vger.kernel.org
Signed-off-by: David Carlier <devnexen@gmail.com>
Link: https://patch.msgid.link/20260409184009.930359-3-devnexen@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
[ inlined missing octep_vf_oq_next_idx() helper as read_idx++ with wraparound ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>