Re: [PATCH] RDMA/siw: bound Read Response placement to the RREAD length

[Jason Gunthorpe <jgg@nvidia.com>]

On Tue, Jun 02, 2026 at 03:47:00PM -0400, Michael Bommarito wrote:
> In drivers/infiniband/sw/siw/siw_qp_rx.c, siw_proc_rresp() places each
> inbound Read Response DDP segment at sge->laddr + wqe->processed and then
> accumulates wqe->processed, but it never checks the running total against
> the sink buffer length on continuation segments. siw_check_sge() resolves
> and validates the sink memory only on the first fragment (the if (!*mem)
> branch), and siw_rresp_check_ntoh() compares the cumulative length against
> wqe->bytes only on the final segment (the !frx->more_ddp_segs guard).
> 
> A connected siw peer that answers an outstanding RREAD with Read Response
> segments that keep the DDP Last flag clear, carrying more total payload
> than the RREAD requested, drives wqe->processed past the validated sink
> buffer; the next siw_rx_data() call writes out of bounds at
> sge->laddr + wqe->processed. siw runs iWARP over ordinary routable TCP,
> so the peer is the remote end of an established RDMA connection and needs
> no local privilege.
> 
> Bound every segment before placement, exactly as siw_proc_send() and
> siw_proc_write() already do for their tagged and untagged paths, and
> terminate the connection with a base-or-bounds DDP error when the
> Read Response would overrun the sink buffer.
> 
> This is the second receive-path length fix for this file. A separate
> change rejects an MPA FPDU length that underflows the per-fragment
> remainder in the header decode; that guard does not cover this case,
> because here each individual segment length is self-consistent and only
> the accumulated placement offset overruns the buffer.
> 
> Fixes: 8b6a361b8c48 ("rdma/siw: receive path")
> Cc: stable@vger.kernel.org
> Assisted-by: Claude:claude-opus-4-8
> Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com>

I made the changes Bernard asked for and applied it to for-next

Thanks,
Jason