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Subject[RFC PATCH 1/4] tracing: Change remove_event_from_tracers() to clear d_subdirs->i_private
Preparation to make the next patches more understandable.

The caller of trace_remove_event_call() is going to free call/files,
this means that every opened id/filter/enable/format file will use
the already freed memory via filp->private_data / inode->i_private.

Change remove_event_from_tracers() to clear ->i_private for every
child. This fixes nothing and even makes the crash more possible,
but this allows to fix the problem later.

Note: this doesn't affect instance_rmdir() paths. It has the similar
problems and they will be fixed separately.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
kernel/trace/trace_events.c | 9 +++++++++
1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 9d2b499..cbd1a57 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1534,6 +1534,14 @@ static void remove_subsystem(struct ftrace_subsystem_dir *dir)
}
}

+static void invalidate_event_file(struct dentry *dir)
+{
+ struct dentry *child;
+ /* ->i_mutex is not needed, nodody can create/remove a file */
+ list_for_each_entry(child, &dir->d_subdirs, d_u.d_child)
+ child->d_inode->i_private = NULL;
+}
+
static void remove_event_from_tracers(struct ftrace_event_call *call)
{
struct ftrace_event_file *file;
@@ -1545,6 +1553,7 @@ static void remove_event_from_tracers(struct ftrace_event_call *call)
continue;

list_del(&file->list);
+ invalidate_event_file(file->dir);
debugfs_remove_recursive(file->dir);
remove_subsystem(file->system);
kmem_cache_free(file_cachep, file);
--
1.5.5.1


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