ACPI: custom_method: fix memory leaks

BugLink: https://bugs.launchpad.net/bugs/1848589

[ Upstream commit 03d1571d ]

In cm_write(), 'buf' is allocated through kzalloc(). In the following
execution, if an error occurs, 'buf' is not deallocated, leading to memory
leaks. To fix this issue, free 'buf' before returning the error.

Fixes: 526b4af4 ("ACPI: Split out custom_method functionality into an own driver")
Signed-off-by: Wenwen Wang <wenwen@cs.uga.edu>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/acpi/custom_method.c

@@ -51,8 +51,10 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf,
 	if ((*ppos > max_size) ||
 	    (*ppos + count > max_size) ||
 	    (*ppos + count < count) ||
-	    (count > uncopied_bytes))
+	    (count > uncopied_bytes)) {
+		kfree(buf);
 		return -EINVAL;
+	}
 
 	if (copy_from_user(buf + (*ppos), user_buf, count)) {
 		kfree(buf);
@@ -72,6 +74,7 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf,
 		add_taint(TAINT_OVERRIDDEN_ACPI_TABLE, LOCKDEP_NOW_UNRELIABLE);
 	}
 
+	kfree(buf);
 	return count;
 }