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[81.108.45.148]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4887e822227sm479479095e9.4.2026.04.05.14.57.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 05 Apr 2026 14:57:58 -0700 (PDT) From: Prathamesh Deshpande To: linux-rdma@vger.kernel.org Cc: prathameshdeshpande7@gmail.com, dledford@redhat.com, haggaie@mellanox.com, jgg@ziepe.ca, leon@kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v8 2/2] IB/mlx5: Fix loopback refcounting leaks and premature disable Date: Sun, 5 Apr 2026 22:57:18 +0100 Message-ID: <20260405215718.19301-3-prathameshdeshpande7@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260405215718.19301-1-prathameshdeshpande7@gmail.com> References: <20260405215718.19301-1-prathameshdeshpande7@gmail.com> Precedence: bulk X-Mailing-List: linux-rdma@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Update mlx5_ib_enable_lb() and mlx5_ib_disable_lb() to ensure symmetric updates of user_td and qps counters. Software state leaks can occur if the force_enable flag is checked before updating counters. Furthermore, the hardware deactivation condition in the original code (user_td == 1) can fail to disable loopback if user_td remains 0, or cause premature deactivation in multi-user scenarios. Fix these by: - Updating counters prior to checking the force_enable gate. - Disabling hardware only when both user_td and qps reach zero. - Implementing a counter rollback if the hardware command fails. Signed-off-by: Prathamesh Deshpande --- v8: - Resubmitted as a fresh, independent thread per maintainer request. - No functional changes since v7. v7: - Split into a separate patch for better bisection. - Moved force_enable check after increments/decrements to fix leaks [Sashiko]. - Updated hardware disable condition to a strict zero-check. v6: - Always update software counters regardless of force_enable to prevent underflows during dynamic unbinding [Sashiko]. - Updated disable condition to user_td <= 1 to prevent HW state leaks on systems without transport domains [Sashiko]. - Rebased on rdma/for-next to resolve baseline application failures. v5: - Moved mutex_init to stage_init_init to prevent crashes on non-ETH hardware. - Implemented 'goto unlock' for concurrency safety in enable/disable paths. - Added atomic rollback and fixed tdn leak. v4: - Moved rollback logic into mlx5_ib_enable_lb() to ensure atomicity within the mutex and prevent race conditions [Sashiko]. v3: - Also call mlx5_ib_disable_lb() on failure to roll back software state/counters [Sashiko]. v2: - Added deallocation of tdn if mlx5_ib_enable_lb() fails [Sashiko]. - Reworded commit message to reflect the functional fix and credit the tool. drivers/infiniband/hw/mlx5/main.c | 37 ++++++++++++++++++------------- 1 file changed, 21 insertions(+), 16 deletions(-) diff --git a/drivers/infiniband/hw/mlx5/main.c b/drivers/infiniband/hw/mlx5/main.c index f49f746bc5bd..fde72ebe721a 100644 --- a/drivers/infiniband/hw/mlx5/main.c +++ b/drivers/infiniband/hw/mlx5/main.c @@ -2009,23 +2009,29 @@ int mlx5_ib_enable_lb(struct mlx5_ib_dev *dev, bool td, bool qp) { int err = 0; - if (dev->lb.force_enable) - return 0; - mutex_lock(&dev->lb.mutex); + if (td) dev->lb.user_td++; if (qp) dev->lb.qps++; - if (dev->lb.user_td == 2 || - dev->lb.qps == 1) { - if (!dev->lb.enabled) { - err = mlx5_nic_vport_update_local_lb(dev->mdev, true); + if (dev->lb.force_enable) + goto unlock; + + if (!dev->lb.enabled && (dev->lb.user_td >= 1 || dev->lb.qps >= 1)) { + err = mlx5_nic_vport_update_local_lb(dev->mdev, true); + if (err) { + if (td) + dev->lb.user_td--; + if (qp) + dev->lb.qps--; + } else { dev->lb.enabled = true; } } +unlock: mutex_unlock(&dev->lb.mutex); return err; @@ -2033,23 +2039,22 @@ int mlx5_ib_enable_lb(struct mlx5_ib_dev *dev, bool td, bool qp) void mlx5_ib_disable_lb(struct mlx5_ib_dev *dev, bool td, bool qp) { - if (dev->lb.force_enable) - return; - mutex_lock(&dev->lb.mutex); + if (td) dev->lb.user_td--; if (qp) dev->lb.qps--; - if (dev->lb.user_td == 1 && - dev->lb.qps == 0) { - if (dev->lb.enabled) { - mlx5_nic_vport_update_local_lb(dev->mdev, false); - dev->lb.enabled = false; - } + if (dev->lb.force_enable) + goto unlock; + + if (dev->lb.enabled && (dev->lb.user_td == 0 && dev->lb.qps == 0)) { + mlx5_nic_vport_update_local_lb(dev->mdev, false); + dev->lb.enabled = false; } +unlock: mutex_unlock(&dev->lb.mutex); } -- 2.43.0