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[2.34.31.72]) by smtp.gmail.com with ESMTPSA id p3-20020a05600c1d8300b0040d1450ca7esm9487652wms.7.2023.12.18.12.28.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 18 Dec 2023 12:28:18 -0800 (PST) From: Marco Pagani To: Moritz Fischer , Wu Hao , Xu Yilun , Tom Rix , Greg Kroah-Hartman Cc: Marco Pagani , linux-kernel@vger.kernel.org, linux-fpga@vger.kernel.org Subject: [RFC PATCH v3 1/2] fpga: add an owner field and use it to take the low-level module's refcount Date: Mon, 18 Dec 2023 21:28:08 +0100 Message-ID: <20231218202809.84253-2-marpagan@redhat.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20231218202809.84253-1-marpagan@redhat.com> References: <20231218202809.84253-1-marpagan@redhat.com> Precedence: bulk X-Mailing-List: linux-fpga@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Add a module owner field to the fpga_manager_ops struct and use it to take the low-level control module's refcount instead of relying on the parent device's driver pointer. Low-level control modules should statically set the owner field to THIS_MODULE. To detect when the owner module pointer becomes stale, set the mops pointer to null during fpga_mgr_unregister() (called by the low-level module exit function) and test it before taking the module's refcount. Use a mutex to avoid a crash that can happen if __fpga_mgr_get() gets suspended between testing the mops pointer and taking the low-level refcount and then resumes when the low-level module has already been freed. Thanks to Xu Yilun for suggesting the locking pattern. Other changes: move put_device() from __fpga_mgr_get() to fpga_mgr_get() and of_fpga_mgr_get() to improve code clarity. Fixes: 654ba4cc0f3e ("fpga manager: ensure lifetime with of_fpga_mgr_get") Signed-off-by: Marco Pagani --- drivers/fpga/fpga-mgr.c | 50 ++++++++++++++++++++++++----------- include/linux/fpga/fpga-mgr.h | 4 +++ 2 files changed, 38 insertions(+), 16 deletions(-) diff --git a/drivers/fpga/fpga-mgr.c b/drivers/fpga/fpga-mgr.c index 06651389c592..a32b7d40080d 100644 --- a/drivers/fpga/fpga-mgr.c +++ b/drivers/fpga/fpga-mgr.c @@ -664,20 +664,20 @@ static struct attribute *fpga_mgr_attrs[] = { }; ATTRIBUTE_GROUPS(fpga_mgr); -static struct fpga_manager *__fpga_mgr_get(struct device *dev) +static struct fpga_manager *__fpga_mgr_get(struct device *mgr_dev) { struct fpga_manager *mgr; - mgr = to_fpga_manager(dev); + mgr = to_fpga_manager(mgr_dev); - if (!try_module_get(dev->parent->driver->owner)) - goto err_dev; + mutex_lock(&mgr->mops_mutex); - return mgr; + if (!mgr->mops || !try_module_get(mgr->mops->owner)) + mgr = ERR_PTR(-ENODEV); -err_dev: - put_device(dev); - return ERR_PTR(-ENODEV); + mutex_unlock(&mgr->mops_mutex); + + return mgr; } static int fpga_mgr_dev_match(struct device *dev, const void *data) @@ -693,12 +693,18 @@ static int fpga_mgr_dev_match(struct device *dev, const void *data) */ struct fpga_manager *fpga_mgr_get(struct device *dev) { - struct device *mgr_dev = class_find_device(&fpga_mgr_class, NULL, dev, - fpga_mgr_dev_match); + struct fpga_manager *mgr; + struct device *mgr_dev; + + mgr_dev = class_find_device(&fpga_mgr_class, NULL, dev, fpga_mgr_dev_match); if (!mgr_dev) return ERR_PTR(-ENODEV); - return __fpga_mgr_get(mgr_dev); + mgr = __fpga_mgr_get(mgr_dev); + if (IS_ERR(mgr)) + put_device(mgr_dev); + + return mgr; } EXPORT_SYMBOL_GPL(fpga_mgr_get); @@ -711,13 +717,18 @@ EXPORT_SYMBOL_GPL(fpga_mgr_get); */ struct fpga_manager *of_fpga_mgr_get(struct device_node *node) { - struct device *dev; + struct fpga_manager *mgr; + struct device *mgr_dev; - dev = class_find_device_by_of_node(&fpga_mgr_class, node); - if (!dev) + mgr_dev = class_find_device_by_of_node(&fpga_mgr_class, node); + if (!mgr_dev) return ERR_PTR(-ENODEV); - return __fpga_mgr_get(dev); + mgr = __fpga_mgr_get(mgr_dev); + if (IS_ERR(mgr)) + put_device(mgr_dev); + + return mgr; } EXPORT_SYMBOL_GPL(of_fpga_mgr_get); @@ -727,7 +738,7 @@ EXPORT_SYMBOL_GPL(of_fpga_mgr_get); */ void fpga_mgr_put(struct fpga_manager *mgr) { - module_put(mgr->dev.parent->driver->owner); + module_put(mgr->mops->owner); put_device(&mgr->dev); } EXPORT_SYMBOL_GPL(fpga_mgr_put); @@ -803,6 +814,7 @@ fpga_mgr_register_full(struct device *parent, const struct fpga_manager_info *in } mutex_init(&mgr->ref_mutex); + mutex_init(&mgr->mops_mutex); mgr->name = info->name; mgr->mops = info->mops; @@ -888,6 +900,12 @@ void fpga_mgr_unregister(struct fpga_manager *mgr) */ fpga_mgr_fpga_remove(mgr); + mutex_lock(&mgr->mops_mutex); + + mgr->mops = NULL; + + mutex_unlock(&mgr->mops_mutex); + device_unregister(&mgr->dev); } EXPORT_SYMBOL_GPL(fpga_mgr_unregister); diff --git a/include/linux/fpga/fpga-mgr.h b/include/linux/fpga/fpga-mgr.h index 54f63459efd6..b4d9413cb444 100644 --- a/include/linux/fpga/fpga-mgr.h +++ b/include/linux/fpga/fpga-mgr.h @@ -162,6 +162,7 @@ struct fpga_manager_info { * @write_complete: set FPGA to operating state after writing is done * @fpga_remove: optional: Set FPGA into a specific state during driver remove * @groups: optional attribute groups. + * @owner: owner module containing the ops. * * fpga_manager_ops are the low level functions implemented by a specific * fpga manager driver. The optional ones are tested for NULL before being @@ -184,6 +185,7 @@ struct fpga_manager_ops { struct fpga_image_info *info); void (*fpga_remove)(struct fpga_manager *mgr); const struct attribute_group **groups; + struct module *owner; }; /* FPGA manager status: Partial/Full Reconfiguration errors */ @@ -201,6 +203,7 @@ struct fpga_manager_ops { * @state: state of fpga manager * @compat_id: FPGA manager id for compatibility check. * @mops: pointer to struct of fpga manager ops + * @mops_mutex: protects mops from low-level module removal * @priv: low level driver private date */ struct fpga_manager { @@ -209,6 +212,7 @@ struct fpga_manager { struct mutex ref_mutex; enum fpga_mgr_states state; struct fpga_compat_id *compat_id; + struct mutex mops_mutex; const struct fpga_manager_ops *mops; void *priv; };