update_last_data_if_empty() is called from tracing_open() with O_TRUNC, tracing_read_pipe() and tracing_buffers_read() without trace_types_lock. Two readers can both pass the LAST_BOOT test and free module_delta twice, and a module notifier can update module_delta while it is being freed. Take trace_types_lock in those paths and keep the callers that already hold it on an unlocked variant. Fixes: 32dc0042528d ("tracing: Reset last-boot buffers when reading out all cpu buffers") Cc: stable@vger.kernel.org Signed-off-by: David Carlier --- kernel/trace/trace.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index d3ffbed9c44b..cf8663c27ae6 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3603,6 +3603,7 @@ static int tracing_single_release_tr(struct inode *inode, struct file *file) return single_release(inode, file); } +static bool __update_last_data_if_empty(struct trace_array *tr); static bool update_last_data_if_empty(struct trace_array *tr); static int tracing_open(struct inode *inode, struct file *file) @@ -4697,7 +4698,7 @@ tracing_set_trace_read(struct file *filp, char __user *ubuf, int tracer_init(struct tracer *t, struct trace_array *tr) { tracing_reset_online_cpus(&tr->array_buffer); - update_last_data_if_empty(tr); + __update_last_data_if_empty(tr); return t->init(tr); } @@ -5371,8 +5372,10 @@ static int tracing_wait_pipe(struct file *filp) return 1; } -static bool update_last_data_if_empty(struct trace_array *tr) +static bool __update_last_data_if_empty(struct trace_array *tr) { + lockdep_assert_held(&trace_types_lock); + if (!(tr->flags & TRACE_ARRAY_FL_LAST_BOOT)) return false; @@ -5387,6 +5390,16 @@ static bool update_last_data_if_empty(struct trace_array *tr) return true; } +static bool update_last_data_if_empty(struct trace_array *tr) +{ + /* Avoid the lock on the read path unless this is a last boot buffer */ + if (!(tr->flags & TRACE_ARRAY_FL_LAST_BOOT)) + return false; + + guard(mutex)(&trace_types_lock); + return __update_last_data_if_empty(tr); +} + /* * Consumer reader. */ @@ -6479,7 +6492,7 @@ int tracing_set_clock(struct trace_array *tr, const char *clockstr) ring_buffer_set_clock(tr->snapshot_buffer.buffer, trace_clocks[i].func); tracing_reset_online_cpus(&tr->snapshot_buffer); #endif - update_last_data_if_empty(tr); + __update_last_data_if_empty(tr); if (tr->scratch && !(tr->flags & TRACE_ARRAY_FL_LAST_BOOT)) { struct trace_scratch *tscratch = tr->scratch; -- 2.55.0