On Tue, 31 Oct 2023 00:00:31 -0400 Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > But the I applied: > > f5ca233e2e66d ("tracing: Increase trace array ref count on enable and filter files") > > And do the above commands again and BOOM! it crashes with: The below patch appears to solve this. Care to test it? -- Steve Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx> --- include/linux/trace_events.h | 4 ++++ kernel/trace/trace.c | 15 +++++++++++++++ kernel/trace/trace.h | 4 ++++ kernel/trace/trace_events.c | 29 +++++++++++++++++++++++++---- kernel/trace/trace_events_filter.c | 3 +++ 5 files changed, 51 insertions(+), 4 deletions(-) diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h index 12207dc6722d..696f8dc4aa53 100644 --- a/include/linux/trace_events.h +++ b/include/linux/trace_events.h @@ -492,6 +492,7 @@ enum { EVENT_FILE_FL_TRIGGER_COND_BIT, EVENT_FILE_FL_PID_FILTER_BIT, EVENT_FILE_FL_WAS_ENABLED_BIT, + EVENT_FILE_FL_FREED_BIT, }; extern struct trace_event_file *trace_get_event_file(const char *instance, @@ -630,6 +631,7 @@ extern int __kprobe_event_add_fields(struct dynevent_cmd *cmd, ...); * TRIGGER_COND - When set, one or more triggers has an associated filter * PID_FILTER - When set, the event is filtered based on pid * WAS_ENABLED - Set when enabled to know to clear trace on module removal + * FREED - File descriptor is freed, all fields should be considered invalid */ enum { EVENT_FILE_FL_ENABLED = (1 << EVENT_FILE_FL_ENABLED_BIT), @@ -643,6 +645,7 @@ enum { EVENT_FILE_FL_TRIGGER_COND = (1 << EVENT_FILE_FL_TRIGGER_COND_BIT), EVENT_FILE_FL_PID_FILTER = (1 << EVENT_FILE_FL_PID_FILTER_BIT), EVENT_FILE_FL_WAS_ENABLED = (1 << EVENT_FILE_FL_WAS_ENABLED_BIT), + EVENT_FILE_FL_FREED = (1 << EVENT_FILE_FL_FREED_BIT), }; struct trace_event_file { @@ -671,6 +674,7 @@ struct trace_event_file { * caching and such. Which is mostly OK ;-) */ unsigned long flags; + atomic_t ref; /* ref count for opened files */ atomic_t sm_ref; /* soft-mode reference counter */ atomic_t tm_ref; /* trigger-mode reference counter */ }; diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 2539cfc20a97..9aebf904ff97 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -4978,6 +4978,20 @@ int tracing_open_file_tr(struct inode *inode, struct file *filp) if (ret) return ret; + mutex_lock(&event_mutex); + + /* Fail if the file is marked for removal */ + if (file->flags & EVENT_FILE_FL_FREED) { + trace_array_put(file->tr); + ret = -ENODEV; + } else { + event_file_get(file); + } + + mutex_unlock(&event_mutex); + if (ret) + return ret; + filp->private_data = inode->i_private; return 0; @@ -4988,6 +5002,7 @@ int tracing_release_file_tr(struct inode *inode, struct file *filp) struct trace_event_file *file = inode->i_private; trace_array_put(file->tr); + event_file_put(file); return 0; } diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index 0e1405abf4f7..4fcd293ecbd4 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -1669,6 +1669,10 @@ extern void event_trigger_unregister(struct event_command *cmd_ops, char *glob, struct event_trigger_data *trigger_data); +extern void event_file_get(struct trace_event_file *file); +extern void event_file_put(struct trace_event_file *file); + + /** * struct event_trigger_ops - callbacks for trace event triggers * diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index 70a029ae3c65..ec86f4894455 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -990,13 +990,33 @@ static void remove_subsystem(struct trace_subsystem_dir *dir) } } +void event_file_get(struct trace_event_file *file) +{ + atomic_inc(&file->ref); +} + +void event_file_put(struct trace_event_file *file) +{ + if (WARN_ON_ONCE(!atomic_read(&file->ref))) { + if (file->flags & EVENT_FILE_FL_FREED) + kmem_cache_free(file_cachep, file); + return; + } + + if (atomic_dec_and_test(&file->ref) && + (file->flags & EVENT_FILE_FL_FREED)) { + kmem_cache_free(file_cachep, file); + } +} + static void remove_event_file_dir(struct trace_event_file *file) { eventfs_remove_dir(file->ei); list_del(&file->list); remove_subsystem(file->system); free_event_filter(file->filter); - kmem_cache_free(file_cachep, file); + file->flags |= EVENT_FILE_FL_FREED; + event_file_put(file); } /* @@ -1369,7 +1389,7 @@ event_enable_read(struct file *filp, char __user *ubuf, size_t cnt, flags = file->flags; mutex_unlock(&event_mutex); - if (!file) + if (!file || flags & EVENT_FILE_FL_FREED) return -ENODEV; if (flags & EVENT_FILE_FL_ENABLED && @@ -1404,7 +1424,7 @@ event_enable_write(struct file *filp, const char __user *ubuf, size_t cnt, ret = -ENODEV; mutex_lock(&event_mutex); file = event_file_data(filp); - if (likely(file)) { + if (likely(file && !(file->flags & EVENT_FILE_FL_FREED))) { printk("update file = %px\n", file); printk("update tr = %px\n", file->tr); ret = tracing_update_buffers(file->tr); @@ -1686,7 +1706,7 @@ event_filter_read(struct file *filp, char __user *ubuf, size_t cnt, mutex_lock(&event_mutex); file = event_file_data(filp); - if (file) + if (file && !(file->flags & EVENT_FILE_FL_FREED)) print_event_filter(file, s); mutex_unlock(&event_mutex); @@ -2905,6 +2925,7 @@ trace_create_new_event(struct trace_event_call *call, atomic_set(&file->tm_ref, 0); INIT_LIST_HEAD(&file->triggers); list_add(&file->list, &tr->events); + event_file_get(file); return file; } diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c index 33264e510d16..0c611b281a5b 100644 --- a/kernel/trace/trace_events_filter.c +++ b/kernel/trace/trace_events_filter.c @@ -2349,6 +2349,9 @@ int apply_event_filter(struct trace_event_file *file, char *filter_string) struct event_filter *filter = NULL; int err; + if (file->flags & EVENT_FILE_FL_FREED) + return -ENODEV; + if (!strcmp(strstrip(filter_string), "0")) { filter_disable(file); filter = event_filter(file); -- 2.42.0