[PATCH v3 5/6] tracing: convert ftrace_regex_write to use copy_strtok_from_user

[Steven Rostedt]

From: Steven Rostedt <srostedt@xxxxxxxxxx>

Impact: clean up

This removes the open coded parsing of a word sent in by the user
and replaces it with copy_strtok_from_user.

Also removes cnt < 0 check since cnt is unsigned.

Also uses (*ppos) += cnt, instead of file->pos += cnt.

Signed-off-by: Steven Rostedt <srostedt@xxxxxxxxxx>
---
 kernel/trace/ftrace.c |  101 +++++++++++++++++++++++++++++--------------------
 1 files changed, 60 insertions(+), 41 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 5a3a06b..963dc14 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1690,11 +1690,13 @@ ftrace_regex_write(struct file *file, const char __user *ubuf,
 		   size_t cnt, loff_t *ppos, int enable)
 {
 	struct ftrace_iterator *iter;
-	char ch;
+	unsigned int copied;
 	size_t read = 0;
+	int len, skip;
 	ssize_t ret;
+	char *buf;
 
-	if (!cnt || cnt < 0)
+	if (!cnt)
 		return 0;
 
 	mutex_lock(&ftrace_regex_lock);
@@ -1710,58 +1712,75 @@ ftrace_regex_write(struct file *file, const char __user *ubuf,
 		iter->buffer_idx = 0;
 	}
 
-	ret = get_user(ch, ubuf++);
-	if (ret)
-		goto out;
-	read++;
-	cnt--;
+	if (iter->flags & FTRACE_ITER_CONT) {
+		/*
+		 * We split on a word, continue from where
+		 * we left off.
+		*/
+		buf = &iter->buffer[iter->buffer_idx];
+		len = FTRACE_BUFF_MAX - iter->buffer_idx;
+		/* do not handle leading spaces. */
+		skip = 0;
+	} else {
+		buf = iter->buffer;
+		/* iter->buffer is size of FTRACE_BUFF_MAX + 1 */
+		len = FTRACE_BUFF_MAX;
+		iter->buffer_idx = 0;
+		/* Skip over any leading spaces */
+		skip = 1;
+	}
 
-	if (!(iter->flags & ~FTRACE_ITER_CONT)) {
-		/* skip white space */
-		while (cnt && isspace(ch)) {
-			ret = get_user(ch, ubuf++);
-			if (ret)
-				goto out;
-			read++;
-			cnt--;
-		}
+	ret = copy_strtok_from_user(buf, ubuf, len, cnt, &copied, SPACES);
+	if (ret < 0)
+		goto out;
 
-		if (isspace(ch)) {
-			file->f_pos += read;
-			ret = read;
-			goto out;
+	if (!skip) {
+		/*
+		 * This is a continuation. If we read spaces, then
+		 * we need to truncate all that was read.
+		 */
+		if (ret > copied) {
+			/* leading spaces were found */
+			iter->buffer[iter->buffer_idx] = 0;
+			/* make it look like we are ready to process */
+			buf = iter->buffer;
+			copied = iter->buffer_idx + 1;
 		}
+	}
 
-		iter->buffer_idx = 0;
+	/* We only read white space. */
+	if (!copied) {
+		(*ppos) += cnt;
+		ret = cnt;
+		goto out;
 	}
 
-	while (cnt && !isspace(ch)) {
-		if (iter->buffer_idx < FTRACE_BUFF_MAX)
-			iter->buffer[iter->buffer_idx++] = ch;
-		else {
+	/* Check if we hit a terminating space */
+	if (buf[copied - 1] != 0) {
+		/* we split on a word */
+		iter->buffer_idx += copied;
+		if (iter->buffer_idx >= FTRACE_BUFF_MAX) {
+			/* too big of a word */
+			iter->buffer_idx = 0;
+			iter->flags &= ~FTRACE_ITER_CONT;
 			ret = -EINVAL;
 			goto out;
 		}
-		ret = get_user(ch, ubuf++);
-		if (ret)
-			goto out;
-		read++;
-		cnt--;
-	}
 
-	if (isspace(ch)) {
-		iter->filtered++;
-		iter->buffer[iter->buffer_idx] = 0;
-		ret = ftrace_process_regex(iter->buffer,
-					   iter->buffer_idx, enable);
-		if (ret)
-			goto out;
-		iter->buffer_idx = 0;
-	} else
+		(*ppos) += cnt;
+		ret = cnt;
 		iter->flags |= FTRACE_ITER_CONT;
+		goto out;
+	}
 
+	read = ret;
 
-	file->f_pos += read;
+	ret = ftrace_process_regex(iter->buffer, iter->buffer_idx, enable);
+	if (ret)
+		goto out;
+	iter->buffer_idx = 0;
+
+	(*ppos) += read;
 
 	ret = read;
  out:
-- 
1.5.6.5

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