tracing: only truncate ftrace files when O_TRUNC is set

The current code will truncate the ftrace files contents if O_APPEND
is not set and the file is opened in write mode. This is incorrect.
It should only truncate the file if O_TRUNC is set. Otherwise
if one of these files is opened by a C program with fopen "r+",
it will incorrectly truncate the file.

Reported-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

3 files changed, 4 insertions, 4 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 1f3ec2afa511..1e1d23c26308 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1662,7 +1662,7 @@ ftrace_regex_open(struct inode *inode, struct file *file, int enable)
 
         mutex_lock(&ftrace_regex_lock);
         if ((file->f_mode & FMODE_WRITE) &&
-            !(file->f_flags & O_APPEND))
+            (file->f_flags & O_TRUNC))
                 ftrace_filter_reset(enable);
 
         if (file->f_mode & FMODE_READ) {
@@ -2577,7 +2577,7 @@ ftrace_graph_open(struct inode *inode, struct file *file)
 
         mutex_lock(&graph_lock);
         if ((file->f_mode & FMODE_WRITE) &&
-            !(file->f_flags & O_APPEND)) {
+            (file->f_flags & O_TRUNC)) {
                 ftrace_graph_count = 0;
                 memset(ftrace_graph_funcs, 0, sizeof(ftrace_graph_funcs));
         }
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 8bc8d8afea6a..d8ef28574aa1 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2031,7 +2031,7 @@ static int tracing_open(struct inode *inode, struct file *file)
 
         /* If this file was open for write, then erase contents */
         if ((file->f_mode & FMODE_WRITE) &&
-            !(file->f_flags & O_APPEND)) {
+            (file->f_flags & O_TRUNC)) {
                 long cpu = (long) inode->i_private;
 
                 if (cpu == TRACE_PIPE_ALL_CPU)
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 53c8fd376a88..23d2972b22d6 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -376,7 +376,7 @@ ftrace_event_seq_open(struct inode *inode, struct file *file)
         const struct seq_operations *seq_ops;
 
         if ((file->f_mode & FMODE_WRITE) &&
-            !(file->f_flags & O_APPEND))
+            (file->f_flags & O_TRUNC))
                 ftrace_clear_events();
 
         seq_ops = inode->i_private;