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>
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 53c8fd3..23d2972 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -376,7 +376,7 @@
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;