Messages in this thread Patch in this message | | | Date | Tue, 23 Jul 2013 22:59:20 +0200 | From | Oleg Nesterov <> | Subject | [PATCH 4/6] tracing: Change f_start() to take event_mutex and verify i_private != NULL |
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trace_format_open() and trace_format_seq_ops are racy, nothing protects ftrace_event_call from trace_remove_event_call().
Change f_start() to take event_mutex and verify i_private != NULL, change f_stop() to drop this lock.
This fixes nothing, but now we can change debugfs_remove("format") callers to nullify ->i_private and fix the the problem.
Note: the usage of event_mutex is sub-optimal but simple, we can change this later.
Signed-off-by: Oleg Nesterov <oleg@redhat.com> --- kernel/trace/trace_events.c | 13 +++++++++---- 1 files changed, 9 insertions(+), 4 deletions(-)
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index 0f081c0..4b43111 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -838,7 +838,7 @@ enum { static void *f_next(struct seq_file *m, void *v, loff_t *pos) { - struct ftrace_event_call *call = m->private; + struct ftrace_event_call *call = event_file_data(m->private); struct list_head *common_head = &ftrace_common_fields; struct list_head *head = trace_get_fields(call); struct list_head *node = v; @@ -870,7 +870,7 @@ static void *f_next(struct seq_file *m, void *v, loff_t *pos) static int f_show(struct seq_file *m, void *v) { - struct ftrace_event_call *call = m->private; + struct ftrace_event_call *call = event_file_data(m->private); struct ftrace_event_field *field; const char *array_descriptor; @@ -923,6 +923,11 @@ static void *f_start(struct seq_file *m, loff_t *pos) void *p = (void *)FORMAT_HEADER; loff_t l = 0; + /* ->stop() is called even if ->start() fails */ + mutex_lock(&event_mutex); + if (!event_file_data(m->private)) + return ERR_PTR(-ENODEV); + while (l < *pos && p) p = f_next(m, p, &l); @@ -931,6 +936,7 @@ static void *f_start(struct seq_file *m, loff_t *pos) static void f_stop(struct seq_file *m, void *p) { + mutex_unlock(&event_mutex); } static const struct seq_operations trace_format_seq_ops = { @@ -942,7 +948,6 @@ static const struct seq_operations trace_format_seq_ops = { static int trace_format_open(struct inode *inode, struct file *file) { - struct ftrace_event_call *call = inode->i_private; struct seq_file *m; int ret; @@ -951,7 +956,7 @@ static int trace_format_open(struct inode *inode, struct file *file) return ret; m = file->private_data; - m->private = call; + m->private = file; return 0; } -- 1.5.5.1
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