net: mana: validate rx_req_idx to prevent out-of-bounds array access

net: mana: validate rx_req_idx to prevent out-of-bounds array access

In mana_hwc_rx_event_handler(), rx_req_idx is derived from
sge->address in DMA-coherent memory. In Confidential VMs
(SEV-SNP/TDX), this memory is shared unencrypted and HW can modify
WQE contents at any time. No bounds check exists on rx_req_idx,
which can lead to an out-of-bounds access into reqs[].

Add bounds check on rx_req_idx in mana_hwc_rx_event_handler() before
using it to index the reqs[] array.

Fixes: ca9c54d2d6a5 ("net: mana: Add a driver for Microsoft Azure Network Adapter (MANA)")
Signed-off-by: Aditya Garg <gargaditya@linux.microsoft.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Link: https://patch.msgid.link/20260520051553.857120-1-gargaditya@linux.microsoft.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>