tracing: protect reader of cmdline output
Impact: fix to one cause of incorrect comm outputs in trace
The spinlock only protected the creation of a comm <=> pid pair.
But it was possible that a reader could look up a pid, and get the
wrong comm because it had no locking.
This also required changing trace_find_cmdline to copy the comm cache
and not just send back a pointer to it.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index efe3202..2796bd2 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -770,25 +770,29 @@
__raw_spin_unlock(&trace_cmdline_lock);
}
-char *trace_find_cmdline(int pid)
+void trace_find_cmdline(int pid, char comm[])
{
- char *cmdline = "<...>";
unsigned map;
- if (!pid)
- return "<idle>";
+ if (!pid) {
+ strcpy(comm, "<idle>");
+ return;
+ }
- if (pid > PID_MAX_DEFAULT)
- goto out;
+ if (pid > PID_MAX_DEFAULT) {
+ strcpy(comm, "<...>");
+ return;
+ }
+ __raw_spin_lock(&trace_cmdline_lock);
map = map_pid_to_cmdline[pid];
if (map >= SAVED_CMDLINES)
goto out;
- cmdline = saved_cmdlines[map];
+ strcpy(comm, saved_cmdlines[map]);
out:
- return cmdline;
+ __raw_spin_unlock(&trace_cmdline_lock);
}
void tracing_record_cmdline(struct task_struct *tsk)