[PATCH AUTOSEL 5.14 04/25] cxl/pci: Introduce cdevm_file_operations
From: Sasha Levin
Date: Mon Sep 13 2021 - 18:34:00 EST
From: Dan Williams <dan.j.williams@xxxxxxxxx>
[ Upstream commit 9cc238c7a526dba9ee8c210fa2828886fc65db66 ]
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@xxxxxxxxx>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
Link: https://lore.kernel.org/r/162792539962.368511.2962268954245340288.stgit@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/cxl/cxlmem.h | 15 ++++++++++
drivers/cxl/pci.c | 65 ++++++++++++++++++++++++++------------------
2 files changed, 53 insertions(+), 27 deletions(-)
diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
index 8f02d02b26b4..0cd463de1342 100644
--- 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 a945c5fda292..f7a5ad5e1f4a 100644
--- 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 @@ static int cxl_mem_setup_regs(struct cxl_mem *cxlm)
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 @@ static struct cxl_memdev *cxl_memdev_alloc(struct cxl_mem *cxlm)
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 @@ static struct cxl_memdev *devm_cxl_add_memdev(struct device *host,
* 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);
--
2.30.2