[PATCH] cxl: Perform NULL check for 'cxl_afu *' at various places in cxl

[Vaibhav Jain <vaibhav@linux.vnet.ibm.com>]

It is possible for a CXL card to have a valid PSL but no valid
AFUs. When this happens we have a valid instance of 'struct cxl'
representing the adapter but with its member 'struct cxl_afu *cxl[]'
as empty. Unfortunately at many placed within cxl code (especially
during an EEH) the elements of this array are passed on to various
other cxl functions. Which may result in kernel oops/panic when this
'struct cxl_afu *' is dereferenced.

So this patch puts a NULL check at the beginning of various cxl
functions that accept 'struct cxl_afu *' as a formal argument and are
called from with a loop of the form:

       for (i = 0; i < adapter->slices; i++) {
       	   	afu = adapter->afu[i];
		/* call some function with 'afu' */
	}

Signed-off-by: Vaibhav Jain <vaibhav@linux.vnet.ibm.com>
---
 drivers/misc/cxl/api.c     |  2 +-
 drivers/misc/cxl/context.c |  3 +++
 drivers/misc/cxl/guest.c   |  4 ++++
 drivers/misc/cxl/main.c    |  3 +++
 drivers/misc/cxl/native.c  |  4 ++++
 drivers/misc/cxl/pci.c     | 13 ++++++++++++-
 6 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/cxl/api.c b/drivers/misc/cxl/api.c
index 753b1a698fc4..3466ef8b9e86 100644
--- a/drivers/misc/cxl/api.c
+++ b/drivers/misc/cxl/api.c
@@ -128,7 +128,7 @@ struct cxl_context *cxl_dev_context_init(struct pci_dev *dev)
 	int rc;
 
 	afu = cxl_pci_to_afu(dev);
-	if (IS_ERR(afu))
+	if (IS_ERR_OR_NULL(afu))
 		return ERR_CAST(afu);
 
 	ctx = cxl_context_alloc();
diff --git a/drivers/misc/cxl/context.c b/drivers/misc/cxl/context.c
index 7ff315ad3692..3957e6e7d187 100644
--- a/drivers/misc/cxl/context.c
+++ b/drivers/misc/cxl/context.c
@@ -303,6 +303,9 @@ void cxl_context_detach_all(struct cxl_afu *afu)
 	struct cxl_context *ctx;
 	int tmp;
 
+	if (afu == NULL)
+		return;
+
 	mutex_lock(&afu->contexts_lock);
 	idr_for_each_entry(&afu->contexts_idr, ctx, tmp) {
 		/*
diff --git a/drivers/misc/cxl/guest.c b/drivers/misc/cxl/guest.c
index f58b4b6c79f2..8165f6f26704 100644
--- a/drivers/misc/cxl/guest.c
+++ b/drivers/misc/cxl/guest.c
@@ -760,6 +760,8 @@ static int activate_afu_directed(struct cxl_afu *afu)
 
 static int guest_afu_activate_mode(struct cxl_afu *afu, int mode)
 {
+	if (afu == NULL)
+		return -EINVAL;
 	if (!mode)
 		return 0;
 	if (!(mode & afu->modes_supported))
@@ -791,6 +793,8 @@ static int deactivate_afu_directed(struct cxl_afu *afu)
 
 static int guest_afu_deactivate_mode(struct cxl_afu *afu, int mode)
 {
+	if (afu == NULL)
+		return -EINVAL;
 	if (!mode)
 		return 0;
 	if (!(mode & afu->modes_supported))
diff --git a/drivers/misc/cxl/main.c b/drivers/misc/cxl/main.c
index c1ba0d42cbc8..296a71ca6f2e 100644
--- a/drivers/misc/cxl/main.c
+++ b/drivers/misc/cxl/main.c
@@ -271,6 +271,9 @@ struct cxl_afu *cxl_alloc_afu(struct cxl *adapter, int slice)
 
 int cxl_afu_select_best_mode(struct cxl_afu *afu)
 {
+	if (afu == NULL)
+		return -EINVAL;
+
 	if (afu->modes_supported & CXL_MODE_DIRECTED)
 		return cxl_ops->afu_activate_mode(afu, CXL_MODE_DIRECTED);
 
diff --git a/drivers/misc/cxl/native.c b/drivers/misc/cxl/native.c
index 1b3d7c65ea3f..d46415b19b71 100644
--- a/drivers/misc/cxl/native.c
+++ b/drivers/misc/cxl/native.c
@@ -971,6 +971,8 @@ static int deactivate_dedicated_process(struct cxl_afu *afu)
 
 static int native_afu_deactivate_mode(struct cxl_afu *afu, int mode)
 {
+	if (afu == NULL)
+		return -EINVAL;
 	if (mode == CXL_MODE_DIRECTED)
 		return deactivate_afu_directed(afu);
 	if (mode == CXL_MODE_DEDICATED)
@@ -980,6 +982,8 @@ static int native_afu_deactivate_mode(struct cxl_afu *afu, int mode)
 
 static int native_afu_activate_mode(struct cxl_afu *afu, int mode)
 {
+	if (!afu)
+		return -EINVAL;
 	if (!mode)
 		return 0;
 	if (!(mode & afu->modes_supported))
diff --git a/drivers/misc/cxl/pci.c b/drivers/misc/cxl/pci.c
index 758842f65a1b..8c87d9fdcf5a 100644
--- a/drivers/misc/cxl/pci.c
+++ b/drivers/misc/cxl/pci.c
@@ -1295,6 +1295,9 @@ static int pci_configure_afu(struct cxl_afu *afu, struct cxl *adapter, struct pc
 {
 	int rc;
 
+	if (afu == NULL)
+		return -EINVAL;
+
 	if ((rc = pci_map_slice_regs(afu, adapter, dev)))
 		return rc;
 
@@ -1341,6 +1344,10 @@ static int pci_configure_afu(struct cxl_afu *afu, struct cxl *adapter, struct pc
 
 static void pci_deconfigure_afu(struct cxl_afu *afu)
 {
+
+	if (afu == NULL)
+		return;
+
 	/*
 	 * It's okay to deconfigure when AFU is already locked, otherwise wait
 	 * until there are no readers
@@ -2078,6 +2085,10 @@ static pci_ers_result_t cxl_vphb_error_detected(struct cxl_afu *afu,
 	pci_ers_result_t result = PCI_ERS_RESULT_NEED_RESET;
 	pci_ers_result_t afu_result = PCI_ERS_RESULT_NEED_RESET;
 
+	/* Force a hotplug if an uninitiaized AFU is encountered */
+	if (afu == NULL)
+		return PCI_ERS_RESULT_DISCONNECT;
+
 	/* There should only be one entry, but go through the list
 	 * anyway
 	 */
@@ -2330,7 +2341,7 @@ static void cxl_pci_resume(struct pci_dev *pdev)
 	for (i = 0; i < adapter->slices; i++) {
 		afu = adapter->afu[i];
 
-		if (afu->phb == NULL)
+		if (afu == NULL || afu->phb == NULL)
 			continue;
 
 		list_for_each_entry(afu_dev, &afu->phb->bus->devices, bus_list) {
-- 
2.14.3