[PATCH rdma-next 2/2] RDMA/irdma: Fix OOB read during CQ MR registration

[Jacob Moroni <jmoroni@google.com>]

Sashiko pointed out an unrelated bug during a previous patch:
https://sashiko.dev/#/patchset/20260512183852.614045-1-jmoroni%40google.com

This change fixes the bug by eliminating the cqmr->split field which
was not being set properly and instead just checks the CQ resize
feature flag directly.

The cqmr->split field essentially tracks whether IRDMA_FEATURE_CQ_RESIZE
is set, but it was not being set until CQ creation time, which is _after_
CQ memory registration (the only other place where it is referenced).

As a result, it would always be false during MR registration and would
therefore cause irdma_handle_q_mem to populate cqmr->shadow even for GEN_2
HW and beyond:

    cqmr->shadow = (dma_addr_t)arr[req->cq_pages];

The issue is that for GEN_2 and beyond, req->cq_pages may be exactly equal
to iwmr->page_cnt and therefore equal to the size of arr, which would cause
an OOB read by one.

Fixes: b48c24c2d710 ("RDMA/irdma: Implement device supported verb APIs")
Signed-off-by: Jacob Moroni <jmoroni@google.com>
---
 drivers/infiniband/hw/irdma/verbs.c | 4 ++--
 drivers/infiniband/hw/irdma/verbs.h | 1 -
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/infiniband/hw/irdma/verbs.c b/drivers/infiniband/hw/irdma/verbs.c
index 670b0e0f9200..4a96e14d1418 100644
--- a/drivers/infiniband/hw/irdma/verbs.c
+++ b/drivers/infiniband/hw/irdma/verbs.c
@@ -2567,7 +2567,6 @@ static int irdma_create_cq(struct ib_cq *ibcq,
 			}
 			cqmr_shadow = &iwpbl_shadow->cq_mr;
 			info.shadow_area_pa = cqmr_shadow->cq_pbl.addr;
-			cqmr->split = true;
 		} else {
 			info.shadow_area_pa = cqmr->shadow;
 		}
@@ -2975,7 +2974,8 @@ static int irdma_handle_q_mem(struct irdma_device *iwdev,
 	case IRDMA_MEMREG_TYPE_CQ:
 		hmc_p = &cqmr->cq_pbl;
 
-		if (!cqmr->split)
+		if (!(iwdev->rf->sc_dev.hw_attrs.uk_attrs.feature_flags &
+		      IRDMA_FEATURE_CQ_RESIZE))
 			cqmr->shadow = (dma_addr_t)arr[req->cq_pages];
 
 		if (lvl)
diff --git a/drivers/infiniband/hw/irdma/verbs.h b/drivers/infiniband/hw/irdma/verbs.h
index aabbb3442098..289ebc9b23ca 100644
--- a/drivers/infiniband/hw/irdma/verbs.h
+++ b/drivers/infiniband/hw/irdma/verbs.h
@@ -65,7 +65,6 @@ struct irdma_hmc_pble {
 struct irdma_cq_mr {
 	struct irdma_hmc_pble cq_pbl;
 	dma_addr_t shadow;
-	bool split;
 };
 
 struct irdma_srq_mr {
-- 
2.54.0.1032.g2f8565e1d1-goog