From 0e48d030e3326c03697db617cb09e53ef291bbec Mon Sep 17 00:00:00 2001 From: Prateek Sood Date: Tue, 10 Dec 2019 09:15:16 +0000 Subject: [PATCH] tracing: Fix lock inversion in trace_event_enable_tgid_record() commit 3a53acf1d9bea11b57c1f6205e3fe73f9d8a3688 upstream. Task T2 Task T3 trace_options_core_write() subsystem_open() mutex_lock(trace_types_lock) mutex_lock(event_mutex) set_tracer_flag() trace_event_enable_tgid_record() mutex_lock(trace_types_lock) mutex_lock(event_mutex) This gives a circular dependency deadlock between trace_types_lock and event_mutex. To fix this invert the usage of trace_types_lock and event_mutex in trace_options_core_write(). This keeps the sequence of lock usage consistent. Link: http://lkml.kernel.org/r/0101016eef175e38-8ca71caf-a4eb-480d-a1e6-6f0bbc015495-000000@us-west-2.amazonses.com Cc: stable@vger.kernel.org Fixes: d914ba37d7145 ("tracing: Add support for recording tgid of tasks") Signed-off-by: Prateek Sood Signed-off-by: Steven Rostedt (VMware) Signed-off-by: Greg Kroah-Hartman --- kernel/trace/trace.c | 8 ++++++++ kernel/trace/trace_events.c | 8 ++++---- 2 files changed, 12 insertions(+), 4 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index b6ff2f84df17..e61aa1c68e99 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -4370,6 +4370,10 @@ int trace_keep_overwrite(struct tracer *tracer, u32 mask, int set) int set_tracer_flag(struct trace_array *tr, unsigned int mask, int enabled) { + if ((mask == TRACE_ITER_RECORD_TGID) || + (mask == TRACE_ITER_RECORD_CMD)) + lockdep_assert_held(&event_mutex); + /* do nothing if flag is already set */ if (!!(tr->trace_flags & mask) == !!enabled) return 0; @@ -4435,6 +4439,7 @@ static int trace_set_options(struct trace_array *tr, char *option) cmp += 2; } + mutex_lock(&event_mutex); mutex_lock(&trace_types_lock); ret = match_string(trace_options, -1, cmp); @@ -4445,6 +4450,7 @@ static int trace_set_options(struct trace_array *tr, char *option) ret = set_tracer_flag(tr, 1 << ret, !neg); mutex_unlock(&trace_types_lock); + mutex_unlock(&event_mutex); /* * If the first trailing whitespace is replaced with '\0' by strstrip, @@ -7457,9 +7463,11 @@ trace_options_core_write(struct file *filp, const char __user *ubuf, size_t cnt, if (val != 0 && val != 1) return -EINVAL; + mutex_lock(&event_mutex); mutex_lock(&trace_types_lock); ret = set_tracer_flag(tr, 1 << index, val); mutex_unlock(&trace_types_lock); + mutex_unlock(&event_mutex); if (ret < 0) return ret; diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index 017f737237e6..ec340e1cbffc 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -327,7 +327,8 @@ void trace_event_enable_cmd_record(bool enable) struct trace_event_file *file; struct trace_array *tr; - mutex_lock(&event_mutex); + lockdep_assert_held(&event_mutex); + do_for_each_event_file(tr, file) { if (!(file->flags & EVENT_FILE_FL_ENABLED)) @@ -341,7 +342,6 @@ void trace_event_enable_cmd_record(bool enable) clear_bit(EVENT_FILE_FL_RECORDED_CMD_BIT, &file->flags); } } while_for_each_event_file(); - mutex_unlock(&event_mutex); } void trace_event_enable_tgid_record(bool enable) @@ -349,7 +349,8 @@ void trace_event_enable_tgid_record(bool enable) struct trace_event_file *file; struct trace_array *tr; - mutex_lock(&event_mutex); + lockdep_assert_held(&event_mutex); + do_for_each_event_file(tr, file) { if (!(file->flags & EVENT_FILE_FL_ENABLED)) continue; @@ -363,7 +364,6 @@ void trace_event_enable_tgid_record(bool enable) &file->flags); } } while_for_each_event_file(); - mutex_unlock(&event_mutex); } static int __ftrace_event_enable_disable(struct trace_event_file *file, -- 2.11.0