tracing: Protect tracer flags with trace_types_lock

Seems that the tracer flags have never been protected from
synchronous writes. Luckily, admins don't usually modify the
tracing flags via two different tasks. But if scripts were to
be used to modify them, then they could get corrupted.

Move the trace_types_lock that protects against tracers changing
to also protect the flags being set.

Cc: stable@vger.kernel.org
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 53df2839bb9396bbb01f63241189400917c5778d..00daf5f8c50b84264a93470dffa7511086ad3439 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2916,6 +2916,8 @@ static int trace_set_options(char *option)
                cmp += 2;
        }
 
+       mutex_lock(&trace_types_lock);
+
        for (i = 0; trace_options[i]; i++) {
                if (strcmp(cmp, trace_options[i]) == 0) {
                        set_tracer_flags(1 << i, !neg);
@@ -2924,11 +2926,10 @@ static int trace_set_options(char *option)
        }
 
        /* If no option could be set, test the specific tracer options */
-       if (!trace_options[i]) {
-               mutex_lock(&trace_types_lock);
+       if (!trace_options[i])
                ret = set_tracer_option(current_trace, cmp, neg);
-               mutex_unlock(&trace_types_lock);
-       }
+
+       mutex_unlock(&trace_types_lock);
 
        return ret;
 }
@@ -4781,7 +4782,10 @@ trace_options_core_write(struct file *filp, const char __user *ubuf, size_t cnt,
 
        if (val != 0 && val != 1)
                return -EINVAL;
+
+       mutex_lock(&trace_types_lock);
        set_tracer_flags(1 << index, val);
+       mutex_unlock(&trace_types_lock);
 
        *ppos += cnt;