tracing: Check the return value of trace_get_user()

Return immediately if trace_get_user() returned failure.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <4AB86614.7020803@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 4 insertions, 5 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index c71e91bf7372..a8fe4782ebad 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2202,7 +2202,7 @@ ftrace_regex_write(struct file *file, const char __user *ubuf,
         struct trace_parser *parser;
         ssize_t ret, read;
 
-        if (!cnt || cnt < 0)
+        if (!cnt)
                 return 0;
 
         mutex_lock(&ftrace_regex_lock);
@@ -2216,7 +2216,7 @@ ftrace_regex_write(struct file *file, const char __user *ubuf,
         parser = &iter->parser;
         read = trace_get_user(parser, ubuf, cnt, ppos);
 
-        if (trace_parser_loaded(parser) &&
+        if (read >= 0 && trace_parser_loaded(parser) &&
             !trace_parser_cont(parser)) {
                 ret = ftrace_process_regex(parser->buffer,
                                            parser->idx, enable);
@@ -2552,8 +2552,7 @@ ftrace_graph_write(struct file *file, const char __user *ubuf,
                    size_t cnt, loff_t *ppos)
 {
         struct trace_parser parser;
-        size_t read = 0;
-        ssize_t ret;
+        ssize_t read, ret;
 
         if (!cnt || cnt < 0)
                 return 0;
@@ -2572,7 +2571,7 @@ ftrace_graph_write(struct file *file, const char __user *ubuf,
 
         read = trace_get_user(&parser, ubuf, cnt, ppos);
 
-        if (trace_parser_loaded((&parser))) {
+        if (read >= 0 && trace_parser_loaded((&parser))) {
                 parser.buffer[parser.idx] = 0;
 
                 /* we allow only one expression at a time */