cxl/pci: Introduce cdevm_file_operations

In preparation for moving cxl_memdev allocation to the core, introduce
cdevm_file_operations to coordinate file operations shutdown relative to
driver data release.

The motivation for moving cxl_memdev allocation to the core (beyond
better file organization of sysfs attributes in core/ and drivers in
cxl/), is that device lifetime is longer than module lifetime. The cxl_pci
module should be free to come and go without needing to coordinate with
devices that need the text associated with cxl_memdev_release() to stay
resident. The move will fix a use after free bug when looping driver
load / unload with CONFIG_DEBUG_KOBJECT_RELEASE=y.

Another motivation for passing in file_operations to the core cxl_memdev
creation flow is to allow for alternate drivers, like unit test code, to
define their own ioctl backends.

Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/162792539962.368511.2962268954245340288.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
index 8f02d02b26b4500097ba443f6308f55f3991b8fd..0cd463de13423491bec8884d730bec3d6638d299 100644 (file)
--- a/drivers/cxl/cxlmem.h
+++ b/drivers/cxl/cxlmem.h
@@ -34,6 +34,21 @@
  */
 #define CXL_MEM_MAX_DEVS 65536
 
+/**
+ * struct cdevm_file_operations - devm coordinated cdev file operations
+ * @fops: file operations that are synchronized against @shutdown
+ * @shutdown: disconnect driver data
+ *
+ * @shutdown is invoked in the devres release path to disconnect any
+ * driver instance data from @dev. It assumes synchronization with any
+ * fops operation that requires driver data. After @shutdown an
+ * operation may only reference @device data.
+ */
+struct cdevm_file_operations {
+       struct file_operations fops;
+       void (*shutdown)(struct device *dev);
+};
+
 /**
  * struct cxl_memdev - CXL bus object representing a Type-3 Memory Device
  * @dev: driver core device object

diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
index a945c5fda29238ff1eb22588b8cc01a8ef84c9e1..f7a5ad5e1f4a73f82188e1dbb6f6f987d9975d13 100644 (file)
--- a/drivers/cxl/pci.c
+++ b/drivers/cxl/pci.c
@@ -806,13 +806,30 @@ static int cxl_memdev_release_file(struct inode *inode, struct file *file)
        return 0;
 }
 
-static const struct file_operations cxl_memdev_fops = {
-       .owner = THIS_MODULE,
-       .unlocked_ioctl = cxl_memdev_ioctl,
-       .open = cxl_memdev_open,
-       .release = cxl_memdev_release_file,
-       .compat_ioctl = compat_ptr_ioctl,
-       .llseek = noop_llseek,
+static struct cxl_memdev *to_cxl_memdev(struct device *dev)
+{
+       return container_of(dev, struct cxl_memdev, dev);
+}
+
+static void cxl_memdev_shutdown(struct device *dev)
+{
+       struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
+
+       down_write(&cxl_memdev_rwsem);
+       cxlmd->cxlm = NULL;
+       up_write(&cxl_memdev_rwsem);
+}
+
+static const struct cdevm_file_operations cxl_memdev_fops = {
+       .fops = {
+               .owner = THIS_MODULE,
+               .unlocked_ioctl = cxl_memdev_ioctl,
+               .open = cxl_memdev_open,
+               .release = cxl_memdev_release_file,
+               .compat_ioctl = compat_ptr_ioctl,
+               .llseek = noop_llseek,
+       },
+       .shutdown = cxl_memdev_shutdown,
 };
 
 static inline struct cxl_mem_command *cxl_mem_find_command(u16 opcode)
@@ -1161,11 +1178,6 @@ free_maps:
        return ret;
 }
 
-static struct cxl_memdev *to_cxl_memdev(struct device *dev)
-{
-       return container_of(dev, struct cxl_memdev, dev);
-}
-
 static void cxl_memdev_release(struct device *dev)
 {
        struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
@@ -1281,24 +1293,22 @@ static const struct device_type cxl_memdev_type = {
        .groups = cxl_memdev_attribute_groups,
 };
 
-static void cxl_memdev_shutdown(struct cxl_memdev *cxlmd)
-{
-       down_write(&cxl_memdev_rwsem);
-       cxlmd->cxlm = NULL;
-       up_write(&cxl_memdev_rwsem);
-}
-
 static void cxl_memdev_unregister(void *_cxlmd)
 {
        struct cxl_memdev *cxlmd = _cxlmd;
        struct device *dev = &cxlmd->dev;
+       struct cdev *cdev = &cxlmd->cdev;
+       const struct cdevm_file_operations *cdevm_fops;
+
+       cdevm_fops = container_of(cdev->ops, typeof(*cdevm_fops), fops);
+       cdevm_fops->shutdown(dev);
 
        cdev_device_del(&cxlmd->cdev, dev);
-       cxl_memdev_shutdown(cxlmd);
        put_device(dev);
 }
 
-static struct cxl_memdev *cxl_memdev_alloc(struct cxl_mem *cxlm)
+static struct cxl_memdev *cxl_memdev_alloc(struct cxl_mem *cxlm,
+                                          const struct file_operations *fops)
 {
        struct pci_dev *pdev = cxlm->pdev;
        struct cxl_memdev *cxlmd;
@@ -1324,7 +1334,7 @@ static struct cxl_memdev *cxl_memdev_alloc(struct cxl_mem *cxlm)
        device_set_pm_not_required(dev);
 
        cdev = &cxlmd->cdev;
-       cdev_init(cdev, &cxl_memdev_fops);
+       cdev_init(cdev, fops);
        return cxlmd;
 
 err:
@@ -1332,15 +1342,16 @@ err:
        return ERR_PTR(rc);
 }
 
-static struct cxl_memdev *devm_cxl_add_memdev(struct device *host,
-                                             struct cxl_mem *cxlm)
+static struct cxl_memdev *
+devm_cxl_add_memdev(struct device *host, struct cxl_mem *cxlm,
+                   const struct cdevm_file_operations *cdevm_fops)
 {
        struct cxl_memdev *cxlmd;
        struct device *dev;
        struct cdev *cdev;
        int rc;
 
-       cxlmd = cxl_memdev_alloc(cxlm);
+       cxlmd = cxl_memdev_alloc(cxlm, &cdevm_fops->fops);
        if (IS_ERR(cxlmd))
                return cxlmd;
 
@@ -1370,7 +1381,7 @@ err:
         * The cdev was briefly live, shutdown any ioctl operations that
         * saw that state.
         */
-       cxl_memdev_shutdown(cxlmd);
+       cdevm_fops->shutdown(dev);
        put_device(dev);
        return ERR_PTR(rc);
 }
@@ -1611,7 +1622,7 @@ static int cxl_mem_probe(struct pci_dev *pdev, const struct pci_device_id *id)
        if (rc)
                return rc;
 
-       cxlmd = devm_cxl_add_memdev(&pdev->dev, cxlm);
+       cxlmd = devm_cxl_add_memdev(&pdev->dev, cxlm, &cxl_memdev_fops);
        if (IS_ERR(cxlmd))
                return PTR_ERR(cxlmd);