[PATCH v2 1/7] platform/x86/amd/hsmp: Serialize ACPI HSMP is_probed with a probe mutex

[Muralidhara M K]

Add hsmp_acpi_probe_mutex and hold it across ACPI probe, remove, and
init_acpi() so concurrent platform probes cannot race the global is_probed
handshake or the one-time socket allocation.  Use lockdep_assert_held() in
init_acpi() to catch incorrect locking under lockdep.

Signed-off-by: Muralidhara M K <muralidhara.mk@xxxxxxx>
---
 drivers/platform/x86/amd/hsmp/acpi.c | 15 +++++++++++++++
 drivers/platform/x86/amd/hsmp/hsmp.c |  9 +++++++++
 2 files changed, 24 insertions(+)

diff --git a/drivers/platform/x86/amd/hsmp/acpi.c b/drivers/platform/x86/amd/hsmp/acpi.c
index 97ed71593bdf..696884a91c22 100644
--- a/drivers/platform/x86/amd/hsmp/acpi.c
+++ b/drivers/platform/x86/amd/hsmp/acpi.c
@@ -18,8 +18,11 @@
 #include <linux/device.h>
 #include <linux/dev_printk.h>
 #include <linux/ioport.h>
+#include <linux/cleanup.h>
+#include <linux/lockdep.h>
 #include <linux/kstrtox.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
 #include <linux/platform_device.h>
 #include <linux/sysfs.h>
 #include <linux/topology.h>
@@ -38,6 +41,8 @@
 
 static struct hsmp_plat_device *hsmp_pdev;
 
+static DEFINE_MUTEX(hsmp_acpi_probe_mutex);
+
 struct hsmp_sys_attr {
 	struct device_attribute dattr;
 	u32 msg_id;
@@ -459,11 +464,17 @@ static ssize_t hsmp_freq_limit_source_show(struct device *dev, struct device_att
 	return len;
 }
 
+/**
+ * init_acpi() - Parse ACPI mailbox resources for one socket and validate HSMP.
+ * @dev: ACPI companion device for this socket.
+ */
 static int init_acpi(struct device *dev)
 {
 	u16 sock_ind;
 	int ret;
 
+	lockdep_assert_held(&hsmp_acpi_probe_mutex);
+
 	ret = hsmp_get_uid(dev, &sock_ind);
 	if (ret)
 		return ret;
@@ -584,6 +595,8 @@ static int hsmp_acpi_probe(struct platform_device *pdev)
 	if (!hsmp_pdev)
 		return -ENOMEM;
 
+	guard(mutex)(&hsmp_acpi_probe_mutex);
+
 	if (!hsmp_pdev->is_probed) {
 		hsmp_pdev->num_sockets = topology_max_packages();
 		if (!hsmp_pdev->num_sockets) {
@@ -619,6 +632,7 @@ static int hsmp_acpi_probe(struct platform_device *pdev)
 
 static void hsmp_acpi_remove(struct platform_device *pdev)
 {
+	mutex_lock(&hsmp_acpi_probe_mutex);
 	/*
 	 * We register only one misc_device even on multi-socket system.
 	 * So, deregister should happen only once.
@@ -627,6 +641,7 @@ static void hsmp_acpi_remove(struct platform_device *pdev)
 		hsmp_misc_deregister();
 		hsmp_pdev->is_probed = false;
 	}
+	mutex_unlock(&hsmp_acpi_probe_mutex);
 }
 
 static struct platform_driver amd_hsmp_driver = {
diff --git a/drivers/platform/x86/amd/hsmp/hsmp.c b/drivers/platform/x86/amd/hsmp/hsmp.c
index 6a26937fc2b5..91be0cdb6af1 100644
--- a/drivers/platform/x86/amd/hsmp/hsmp.c
+++ b/drivers/platform/x86/amd/hsmp/hsmp.c
@@ -223,6 +223,15 @@ int hsmp_send_message(struct hsmp_message *msg)
 	sock_ind = array_index_nospec(msg->sock_ind, hsmp_pdev.num_sockets);
 	sock = &hsmp_pdev.sock[sock_ind];
 
+	/*
+	 * A slot exists for every possible socket, but its state (including
+	 * hsmp_sem) is only initialized once that socket has actually been
+	 * probed.  Reject messages aimed at a socket that was never brought
+	 * up so we never operate on a zero-initialized semaphore.
+	 */
+	if (!sock->dev)
+		return -ENODEV;
+
 	ret = down_interruptible(&sock->hsmp_sem);
 	if (ret < 0)
 		return ret;
-- 
2.43.0