fix tt_command_write()

1) unbalanced debugfs_file_get().  Not needed in the first place -
file_operations are accessed only via debugfs_create_file(), so
debugfs wrappers will take care of that itself.

2) kmalloc() for a buffer used only for duration of a function is not
a problem, but for a buffer no longer than 16 bytes?

3) strstr() is for finding substrings; for finding a character there's
strchr().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: "Rafael J. Wysocki" <rafael@kernel.org>
Link: https://lore.kernel.org/r/20250702212542.GH3406663@ZenIV
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 10 insertions, 20 deletions

diff --git a/drivers/thermal/testing/command.c b/drivers/thermal/testing/command.c
index ba11d70e8021..1159ecea57e7 100644
--- a/drivers/thermal/testing/command.c
+++ b/drivers/thermal/testing/command.c
@@ -139,31 +139,21 @@ static int tt_command_exec(int index, const char *arg)
 	return ret;
 }
 
-static ssize_t tt_command_process(struct dentry *dentry, const char __user *user_buf,
-				  size_t count)
+static ssize_t tt_command_process(char *s)
 {
-	char *buf __free(kfree);
 	char *arg;
 	int i;
 
-	buf = kmalloc(count + 1, GFP_KERNEL);
-	if (!buf)
-		return -ENOMEM;
+	strim(s);
 
-	if (copy_from_user(buf, user_buf, count))
-		return -EFAULT;
-
-	buf[count] = '\0';
-	strim(buf);
-
-	arg = strstr(buf, ":");
+	arg = strchr(s, ':');
 	if (arg) {
 		*arg = '\0';
 		arg++;
 	}
 
 	for (i = 0; i < ARRAY_SIZE(tt_command_strings); i++) {
-		if (!strcmp(buf, tt_command_strings[i]))
+		if (!strcmp(s, tt_command_strings[i]))
 			return tt_command_exec(i, arg);
 	}
 
@@ -173,20 +163,20 @@ static ssize_t tt_command_process(struct dentry *dentry, const char __user *user
 static ssize_t tt_command_write(struct file *file, const char __user *user_buf,
 				size_t count, loff_t *ppos)
 {
-	struct dentry *dentry = file->f_path.dentry;
+	char buf[TT_COMMAND_SIZE];
 	ssize_t ret;
 
 	if (*ppos)
 		return -EINVAL;
 
-	if (count + 1 > TT_COMMAND_SIZE)
+	if (count > TT_COMMAND_SIZE - 1)
 		return -E2BIG;
 
-	ret = debugfs_file_get(dentry);
-	if (unlikely(ret))
-		return ret;
+	if (copy_from_user(buf, user_buf, count))
+		return -EFAULT;
+	buf[count] = '\0';
 
-	ret = tt_command_process(dentry, user_buf, count);
+	ret = tt_command_process(buf);
 	if (ret)
 		return ret;