[PATCH] PCI/doe: Fix work struct declaration

[ira . weiny]

From: Ira Weiny <ira.weiny@xxxxxxxxx>

The callers of pci_doe_submit_task() allocate the pci_doe_task on the
stack.  This causes the work structure to be allocated on the stack
without pci_doe_submit_task() knowing.  Work item initialization needs
to be done with either INIT_WORK_ONSTACK() or INIT_WORK() depending on
how the work item is allocated.

Jonathan suggested creating doe task allocation macros such as
DECLARE_CDAT_DOE_TASK_ONSTACK().[1]  The issue with this is the work
function is not known to the callers and must be initialized correctly.

A follow up suggestion was to have an internal 'pci_doe_work' item
allocated by pci_doe_submit_task().[2]  This requires an allocation which
could restrict the context where tasks are used.

Compromise with an intermediate step to initialize the task struct with
a new call pci_doe_init_task() which must be called prior to submit
task.

[1] https://lore.kernel.org/linux-cxl/20221014151045.24781-1-Jonathan.Cameron@xxxxxxxxxx/T/#m88a7f50dcce52f30c8bf5c3dcc06fa9843b54a2d
[2] https://lore.kernel.org/linux-cxl/20221014151045.24781-1-Jonathan.Cameron@xxxxxxxxxx/T/#m63c636c5135f304480370924f4d03c00357be667

Cc: Bjorn Helgaas <helgaas@xxxxxxxxxx>
Reported-by: Gregory Price <gregory.price@xxxxxxxxxxxx>
Reported-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
Suggested-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx>
---
 drivers/cxl/core/pci.c  |  2 ++
 drivers/pci/doe.c       | 14 ++++++++++++--
 include/linux/pci-doe.h |  8 +++++---
 3 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
index 9240df53ed87..a19c1fa0e2f4 100644
--- a/drivers/cxl/core/pci.c
+++ b/drivers/cxl/core/pci.c
@@ -525,6 +525,7 @@ static int cxl_cdat_get_length(struct device *dev,
 	DECLARE_CDAT_DOE_TASK(CDAT_DOE_REQ(0), t);
 	int rc;
 
+	pci_doe_init_task(cdat_doe, &t.task, true);
 	rc = pci_doe_submit_task(cdat_doe, &t.task);
 	if (rc < 0) {
 		dev_err(dev, "DOE submit failed: %d", rc);
@@ -554,6 +555,7 @@ static int cxl_cdat_read_table(struct device *dev,
 		u32 *entry;
 		int rc;
 
+		pci_doe_init_task(cdat_doe, &t.task, true);
 		rc = pci_doe_submit_task(cdat_doe, &t.task);
 		if (rc < 0) {
 			dev_err(dev, "DOE submit failed: %d", rc);
diff --git a/drivers/pci/doe.c b/drivers/pci/doe.c
index e402f05068a5..cabeae4ae955 100644
--- a/drivers/pci/doe.c
+++ b/drivers/pci/doe.c
@@ -319,6 +319,7 @@ static int pci_doe_discovery(struct pci_doe_mb *doe_mb, u8 *index, u16 *vid,
 	};
 	int rc;
 
+	pci_doe_init_task(doe_mb, &task, true);
 	rc = pci_doe_submit_task(doe_mb, &task);
 	if (rc < 0)
 		return rc;
@@ -495,6 +496,14 @@ bool pci_doe_supports_prot(struct pci_doe_mb *doe_mb, u16 vid, u8 type)
 }
 EXPORT_SYMBOL_GPL(pci_doe_supports_prot);
 
+void pci_doe_init_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task,
+		       bool onstack)
+{
+	task->doe_mb = doe_mb;
+	__INIT_WORK(&task->work, doe_statemachine_work, onstack);
+}
+EXPORT_SYMBOL_GPL(pci_doe_init_task);
+
 /**
  * pci_doe_submit_task() - Submit a task to be processed by the state machine
  *
@@ -517,6 +526,9 @@ int pci_doe_submit_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task)
 	if (!pci_doe_supports_prot(doe_mb, task->prot.vid, task->prot.type))
 		return -EINVAL;
 
+	if (WARN_ON_ONCE(task->work.func != doe_statemachine_work))
+		return -EINVAL;
+
 	/*
 	 * DOE requests must be a whole number of DW and the response needs to
 	 * be big enough for at least 1 DW
@@ -528,8 +540,6 @@ int pci_doe_submit_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task)
 	if (test_bit(PCI_DOE_FLAG_DEAD, &doe_mb->flags))
 		return -EIO;
 
-	task->doe_mb = doe_mb;
-	INIT_WORK(&task->work, doe_statemachine_work);
 	queue_work(doe_mb->work_queue, &task->work);
 	return 0;
 }
diff --git a/include/linux/pci-doe.h b/include/linux/pci-doe.h
index ed9b4df792b8..457fc0e53d64 100644
--- a/include/linux/pci-doe.h
+++ b/include/linux/pci-doe.h
@@ -31,8 +31,8 @@ struct pci_doe_mb;
  * @rv: Return value.  Length of received response or error (bytes)
  * @complete: Called when task is complete
  * @private: Private data for the consumer
- * @work: Used internally by the mailbox
- * @doe_mb: Used internally by the mailbox
+ * @work: Used internally by the mailbox [see pci_doe_init_task()]
+ * @doe_mb: Used internally by the mailbox [see pci_doe_init_task()]
  *
  * The payload sizes and rv are specified in bytes with the following
  * restrictions concerning the protocol.
@@ -53,7 +53,7 @@ struct pci_doe_task {
 	void (*complete)(struct pci_doe_task *task);
 	void *private;
 
-	/* No need for the user to initialize these fields */
+	/* Call pci_doe_init_task() for these */
 	struct work_struct work;
 	struct pci_doe_mb *doe_mb;
 };
@@ -72,6 +72,8 @@ struct pci_doe_task {
 
 struct pci_doe_mb *pcim_doe_create_mb(struct pci_dev *pdev, u16 cap_offset);
 bool pci_doe_supports_prot(struct pci_doe_mb *doe_mb, u16 vid, u8 type);
+void pci_doe_init_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task,
+		       bool onstack);
 int pci_doe_submit_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task);
 
 #endif

base-commit: 30a0b95b1335e12efef89dd78518ed3e4a71a763
-- 
2.37.2