From: Jakob Koschel Date: Wed, 27 Apr 2022 17:07:34 +0000 (+0200) Subject: tracing: Remove check of list iterator against head past the loop body X-Git-Tag: v6.1-rc5~1217^2~23 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=ba27d8555867b0e02e15709f4ddb79aec5cf2efc;p=platform%2Fkernel%2Flinux-starfive.git tracing: Remove check of list iterator against head past the loop body When list_for_each_entry() completes the iteration over the whole list without breaking the loop, the iterator value will be a bogus pointer computed based on the head element. While it is safe to use the pointer to determine if it was computed based on the head element, either with list_entry_is_head() or &pos->member == head, using the iterator variable after the loop should be avoided. In preparation to limit the scope of a list iterator to the list traversal loop, use a dedicated pointer to point to the found element [1]. Link: https://lkml.kernel.org/r/20220427170734.819891-5-jakobkoschel@gmail.com Cc: Ingo Molnar Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/ Signed-off-by: Jakob Koschel Signed-off-by: Steven Rostedt (Google) --- diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 4f1d2f5..5c465e7 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -4560,8 +4560,8 @@ register_ftrace_function_probe(char *glob, struct trace_array *tr, struct ftrace_probe_ops *probe_ops, void *data) { + struct ftrace_func_probe *probe = NULL, *iter; struct ftrace_func_entry *entry; - struct ftrace_func_probe *probe; struct ftrace_hash **orig_hash; struct ftrace_hash *old_hash; struct ftrace_hash *hash; @@ -4580,11 +4580,13 @@ register_ftrace_function_probe(char *glob, struct trace_array *tr, mutex_lock(&ftrace_lock); /* Check if the probe_ops is already registered */ - list_for_each_entry(probe, &tr->func_probes, list) { - if (probe->probe_ops == probe_ops) + list_for_each_entry(iter, &tr->func_probes, list) { + if (iter->probe_ops == probe_ops) { + probe = iter; break; + } } - if (&probe->list == &tr->func_probes) { + if (!probe) { probe = kzalloc(sizeof(*probe), GFP_KERNEL); if (!probe) { mutex_unlock(&ftrace_lock); @@ -4702,9 +4704,9 @@ int unregister_ftrace_function_probe_func(char *glob, struct trace_array *tr, struct ftrace_probe_ops *probe_ops) { + struct ftrace_func_probe *probe = NULL, *iter; struct ftrace_ops_hash old_hash_ops; struct ftrace_func_entry *entry; - struct ftrace_func_probe *probe; struct ftrace_glob func_g; struct ftrace_hash **orig_hash; struct ftrace_hash *old_hash; @@ -4732,11 +4734,13 @@ unregister_ftrace_function_probe_func(char *glob, struct trace_array *tr, mutex_lock(&ftrace_lock); /* Check if the probe_ops is already registered */ - list_for_each_entry(probe, &tr->func_probes, list) { - if (probe->probe_ops == probe_ops) + list_for_each_entry(iter, &tr->func_probes, list) { + if (iter->probe_ops == probe_ops) { + probe = iter; break; + } } - if (&probe->list == &tr->func_probes) + if (!probe) goto err_unlock_ftrace; ret = -EINVAL; diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c index b045fa9..7d44785 100644 --- a/kernel/trace/trace_eprobe.c +++ b/kernel/trace/trace_eprobe.c @@ -648,7 +648,7 @@ static struct trace_event_functions eprobe_funcs = { static int disable_eprobe(struct trace_eprobe *ep, struct trace_array *tr) { - struct event_trigger_data *trigger; + struct event_trigger_data *trigger = NULL, *iter; struct trace_event_file *file; struct eprobe_data *edata; @@ -656,14 +656,16 @@ static int disable_eprobe(struct trace_eprobe *ep, if (!file) return -ENOENT; - list_for_each_entry(trigger, &file->triggers, list) { - if (!(trigger->flags & EVENT_TRIGGER_FL_PROBE)) + list_for_each_entry(iter, &file->triggers, list) { + if (!(iter->flags & EVENT_TRIGGER_FL_PROBE)) continue; - edata = trigger->private_data; - if (edata->ep == ep) + edata = iter->private_data; + if (edata->ep == ep) { + trigger = iter; break; + } } - if (list_entry_is_head(trigger, &file->triggers, list)) + if (!trigger) return -ENODEV; list_del_rcu(&trigger->list); diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index e4a4420..78f313b 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -2279,8 +2279,8 @@ static struct dentry * event_subsystem_dir(struct trace_array *tr, const char *name, struct trace_event_file *file, struct dentry *parent) { + struct event_subsystem *system, *iter; struct trace_subsystem_dir *dir; - struct event_subsystem *system; struct dentry *entry; /* First see if we did not already create this dir */ @@ -2294,13 +2294,13 @@ event_subsystem_dir(struct trace_array *tr, const char *name, } /* Now see if the system itself exists. */ - list_for_each_entry(system, &event_subsystems, list) { - if (strcmp(system->name, name) == 0) + system = NULL; + list_for_each_entry(iter, &event_subsystems, list) { + if (strcmp(iter->name, name) == 0) { + system = iter; break; + } } - /* Reset system variable when not found */ - if (&system->list == &event_subsystems) - system = NULL; dir = kmalloc(sizeof(*dir), GFP_KERNEL); if (!dir)