Re: [PATCH v2] RDMA/rxe: validate inline sge_offset in finish_packet() before indexing inline_data[]

[sashiko-bot@kernel.org]

> For a user QP, rxe_post_send() takes the qp->is_user branch and
> never runs init_send_wqe(), so
> dma.length/resid/num_sge/cur_sge/sge_offset all come straight from
> the mmap'd SQ ring. In the inline send path finish_packet() uses
> sge_offset directly as an index:
> 
> 	u8 *tmp = &wqe->dma.inline_data[wqe->dma.sge_offset];
> 	memcpy(payload_addr(pkt), tmp, payload);
> 
> inline_data is a flex array whose capacity is qp->sq.max_inline, but
> sge_offset is a u32 from user space, so the source pointer is
> displaced arbitrarily past the WQE and the memcpy reads out of
> bounds.
> commit 126c757e4cd4 ("RDMA/rxe: Validate num_sge/cur_sge before indexing wqe->dma.sge[]")
> added num_sge/cur_sge checks on the send path but not sge_offset, the
> third attacker-controlled index in the same struct.
> 
> Read sge_offset once with READ_ONCE() and bound it (and the payload
> that follows it) by qp->sq.max_inline before indexing, so the value
> that is validated is the value that is used.
> 
> Fixes: 8700e3e7c485 ("Soft RoCE driver")
> Cc: stable@vger.kernel.org
> Signed-off-by: Youngsung Ahn <ays511.kr@gmail.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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