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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: Pr0pjSnGBHTJVZ39x0SdV5A7aPVGJSkYpgpCi2b2LUkxy+yDnBEN0iD6+D8JFURHy3tS4cHKI0G3yujSFsTG5USgBIsXhPNGHON7vU46A6vGHPesMVzfpKex1EPTilwFZ60Htath5iodl8AzkdBbPzbgBKCdMlRancjJ7LOx5j2AenReKGiRWGYJvocItBtg12nmSv028e1jns38mqD/nzPcgiO2M6hcdmHA1cn7SYvLMSuKE3lD68EUJ19osp0/qqgTaPekAhE8G9FoXGY6BpD5LX5pU8ubkEy2T1+oD7/63KkjgwG8XG0X6+DfEQ22ZXk6IPQExavBPlh5LqZERNUH3X9F81F7O1j3ZjQAQYWXNH3N0k6K81KGn7iLlaZ95k9X+NdHNbxekaGaXWwEVTEV7nKLl9h1Akq0uj38baE7xIjeZ2cpamf0Jmv8to+l X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Sep 2026 15:34:18.2614 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 90366cab-3b1d-4165-7fbe-08df133ece84 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.161];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: MW1PEPF0001615D.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS2PR12MB9749 From: Yishai Hadas __mlx5_ib_cq_clean() sweeps the CQ backwards from the producer index down to the consumer index: while ((int) --prod_index - (int) cq->mcq.cons_index >= 0) Both indexes are free running u32 counters, so the comparison has to be done modulo 2^32. Casting each operand to int and subtracting does not do that: the subtraction overflows whenever the two indexes straddle 2^31, which is undefined behaviour, and a compiler that assumes signed overflow cannot occur is free to discard the subtraction and fold the expression into a plain signed comparison. That comparison is not wraparound safe. The kernel is built with -fno-strict-overflow, so gcc and clang both retain the subtraction today and the generated code is unaffected; there is no known user-visible impact from the current code. Still, correctness here shouldn't depend on that build flag. Replace the loop with a plain unsigned equality check instead. while (prod_index != cq->mcq.cons_index) { --prod_index; ... The preceding forward scan starts prod_index at cons_index and stops no later than cons_index + cq->ibcq.cqe, so the two indexes are at most cq->ibcq.cqe apart. Decrementing prod_index reaches cons_index in exactly that many iterations regardless of whether either counter has wrapped, because the loop no longer compares magnitudes at all. Signed-off-by: Yishai Hadas Signed-off-by: Edward Srouji --- drivers/infiniband/hw/mlx5/cq.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/infiniband/hw/mlx5/cq.c b/drivers/infiniband/hw/mlx5/cq.c index 49b4bf148a4a017079c93a9b267690bf3a23169a..51892911e32a4b1c90c80e36c523e1906feeab8b 100644 --- a/drivers/infiniband/hw/mlx5/cq.c +++ b/drivers/infiniband/hw/mlx5/cq.c @@ -1169,7 +1169,8 @@ void __mlx5_ib_cq_clean(struct mlx5_ib_cq *cq, u32 rsn, struct mlx5_ib_srq *srq) /* Now sweep backwards through the CQ, removing CQ entries * that match our QP by copying older entries on top of them. */ - while ((int) --prod_index - (int) cq->mcq.cons_index >= 0) { + while (prod_index != cq->mcq.cons_index) { + --prod_index; cqe = get_cqe(cq, prod_index & cq->ibcq.cqe); cqe64 = (cq->mcq.cqe_sz == 64) ? cqe : cqe + 64; if (is_equal_rsn(cqe64, rsn)) { -- 2.49.0