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authorSteven Rostedt <srostedt@redhat.com>2009-05-06 21:54:09 -0400
committerSteven Rostedt <rostedt@goodmis.org>2009-05-06 23:11:41 -0400
commit9456f0fa6d3cb944d3b9fc31c9a244e0362c26ea (patch)
tree9e6e97199f63c786a79966a5938873a98591e10c /kernel/trace/trace.c
parent71e1c8ac42ae4038ddb1367cce7097ab868dc532 (diff)
tracing: reset ring buffer when removing modules with events
Li Zefan found that there's a race using the event ids of events and modules. When a module is loaded, an event id is incremented. We only have 16 bits for event ids (65536) and there is a possible (but highly unlikely) race that we could load and unload a module that registers events so many times that the event id counter overflows. When it overflows, it then restarts and goes looking for available ids. An id is available if it was added by a module and released. The race is if you have one module add an id, and then is removed. Another module loaded can use that same event id. But if the old module still had events in the ring buffer, the new module's call back would get bogus data. At best (and most likely) the output would just be garbage. But if the module for some reason used pointers (not recommended) then this could potentially crash. The safest thing to do is just reset the ring buffer if a module that registered events is removed. [ Impact: prevent unpredictable results of event id overflows ] Reported-by: Li Zefan <lizf@cn.fujitsu.com> LKML-Reference: <49FEAFD0.30106@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace/trace.c')
-rw-r--r--kernel/trace/trace.c10
1 files changed, 10 insertions, 0 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 4164a344e72a..dd40d2320346 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -639,6 +639,16 @@ void tracing_reset_online_cpus(struct trace_array *tr)
639 tracing_reset(tr, cpu); 639 tracing_reset(tr, cpu);
640} 640}
641 641
642void tracing_reset_current(int cpu)
643{
644 tracing_reset(&global_trace, cpu);
645}
646
647void tracing_reset_current_online_cpus(void)
648{
649 tracing_reset_online_cpus(&global_trace);
650}
651
642#define SAVED_CMDLINES 128 652#define SAVED_CMDLINES 128
643#define NO_CMDLINE_MAP UINT_MAX 653#define NO_CMDLINE_MAP UINT_MAX
644static unsigned map_pid_to_cmdline[PID_MAX_DEFAULT+1]; 654static unsigned map_pid_to_cmdline[PID_MAX_DEFAULT+1];