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oleg-nesterovgregkh
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tracing: Change remove_event_file_dir() to clear "d_subdirs"->i_private
commit bf682c3159c4d298d1126a56793ed3f5e80395f7 upstream. Change remove_event_file_dir() to clear ->i_private for every file we are going to remove. We need to check file->dir != NULL because event_create_dir() can fail. debugfs_remove_recursive(NULL) is fine but the patch moves it under the same check anyway for readability. spin_lock(d_lock) and "d_inode != NULL" check are not needed afaics, but I do not understand this code enough. tracing_open_generic_file() and tracing_release_generic_file() can go away, ftrace_enable_fops and ftrace_event_filter_fops() use tracing_open_generic() but only to check tracing_disabled. This fixes all races with event_remove() or instance_delete(). f_op->read/write/whatever can never use the freed file/call, all event/* files were changed to check and use ->i_private under event_mutex. Note: this doesn't not fix other problems, event_remove() can destroy the active ftrace_event_call, we need more changes but those changes are completely orthogonal. Link: http://lkml.kernel.org/r/[email protected] Reviewed-by: Masami Hiramatsu <[email protected]> Signed-off-by: Oleg Nesterov <[email protected]> Signed-off-by: Steven Rostedt <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]>
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kernel/trace/trace_events.c

Lines changed: 15 additions & 32 deletions
Original file line numberDiff line numberDiff line change
@@ -426,41 +426,25 @@ static void *event_file_data(struct file *filp)
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427427
static void remove_event_file_dir(struct ftrace_event_file *file)
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{
429+
struct dentry *dir = file->dir;
430+
struct dentry *child;
431+
432+
if (dir) {
433+
spin_lock(&dir->d_lock); /* probably unneeded */
434+
list_for_each_entry(child, &dir->d_subdirs, d_u.d_child) {
435+
if (child->d_inode) /* probably unneeded */
436+
child->d_inode->i_private = NULL;
437+
}
438+
spin_unlock(&dir->d_lock);
439+
440+
debugfs_remove_recursive(dir);
441+
}
442+
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list_del(&file->list);
430-
debugfs_remove_recursive(file->dir);
431444
remove_subsystem(file->system);
432445
kmem_cache_free(file_cachep, file);
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}
434447

435-
/*
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* Open and update trace_array ref count.
437-
* Must have the current trace_array passed to it.
438-
*/
439-
static int tracing_open_generic_file(struct inode *inode, struct file *filp)
440-
{
441-
struct ftrace_event_file *file = inode->i_private;
442-
struct trace_array *tr = file->tr;
443-
int ret;
444-
445-
if (trace_array_get(tr) < 0)
446-
return -ENODEV;
447-
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ret = tracing_open_generic(inode, filp);
449-
if (ret < 0)
450-
trace_array_put(tr);
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return ret;
452-
}
453-
454-
static int tracing_release_generic_file(struct inode *inode, struct file *filp)
455-
{
456-
struct ftrace_event_file *file = inode->i_private;
457-
struct trace_array *tr = file->tr;
458-
459-
trace_array_put(tr);
460-
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return 0;
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}
463-
464448
/*
465449
* __ftrace_set_clr_event(NULL, NULL, NULL, set) will set/unset all events.
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*/
@@ -1303,10 +1287,9 @@ static const struct file_operations ftrace_set_event_fops = {
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};
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13051289
static const struct file_operations ftrace_enable_fops = {
1306-
.open = tracing_open_generic_file,
1290+
.open = tracing_open_generic,
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.read = event_enable_read,
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.write = event_enable_write,
1309-
.release = tracing_release_generic_file,
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.llseek = default_llseek,
13111294
};
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