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authorNamhyung Kim <namhyung@kernel.org>2017-04-17 11:44:27 +0900
committerSteven Rostedt (VMware) <rostedt@goodmis.org>2017-04-17 16:44:23 -0400
commitd879d0b8c183aabeb9a65eba91f3f9e3c7e7b905 (patch)
parent82cc4fc2e70ec5baeff8f776f2773abc8b2cc0ae (diff)
ftrace: Fix function pid filter on instances
When function tracer has a pid filter, it adds a probe to sched_switch to track if current task can be ignored. The probe checks the ftrace_ignore_pid from current tr to filter tasks. But it misses to delete the probe when removing an instance so that it can cause a crash due to the invalid tr pointer (use-after-free). This is easily reproducible with the following: # cd /sys/kernel/debug/tracing # mkdir instances/buggy # echo $$ > instances/buggy/set_ftrace_pid # rmdir instances/buggy ============================================================================ BUG: KASAN: use-after-free in ftrace_filter_pid_sched_switch_probe+0x3d/0x90 Read of size 8 by task kworker/0:1/17 CPU: 0 PID: 17 Comm: kworker/0:1 Tainted: G B 4.11.0-rc3 #198 Call Trace: dump_stack+0x68/0x9f kasan_object_err+0x21/0x70 kasan_report.part.1+0x22b/0x500 ? ftrace_filter_pid_sched_switch_probe+0x3d/0x90 kasan_report+0x25/0x30 __asan_load8+0x5e/0x70 ftrace_filter_pid_sched_switch_probe+0x3d/0x90 ? fpid_start+0x130/0x130 __schedule+0x571/0xce0 ... To fix it, use ftrace_clear_pids() to unregister the probe. As instance_rmdir() already updated ftrace codes, it can just free the filter safely. Link: http://lkml.kernel.org/r/20170417024430.21194-2-namhyung@kernel.org Fixes: 0c8916c34203 ("tracing: Add rmdir to remove multibuffer instances") Cc: Ingo Molnar <mingo@kernel.org> Cc: stable@vger.kernel.org Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Namhyung Kim <namhyung@kernel.org> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
3 files changed, 12 insertions, 0 deletions
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 27bb2e61276e..dd3e91d68dc7 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -5566,6 +5566,15 @@ static void clear_ftrace_pids(struct trace_array *tr)
+void ftrace_clear_pids(struct trace_array *tr)
+ mutex_lock(&ftrace_lock);
+ clear_ftrace_pids(tr);
+ mutex_unlock(&ftrace_lock);
static void ftrace_pid_reset(struct trace_array *tr)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index f35109514a01..d484452ae648 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -7402,6 +7402,7 @@ static int instance_rmdir(const char *name)
+ ftrace_clear_pids(tr);
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index ae1cce91fead..d19d52d600d6 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -896,6 +896,7 @@ int using_ftrace_ops_list_func(void);
void ftrace_init_tracefs(struct trace_array *tr, struct dentry *d_tracer);
void ftrace_init_tracefs_toplevel(struct trace_array *tr,
struct dentry *d_tracer);
+void ftrace_clear_pids(struct trace_array *tr);
static inline int ftrace_trace_task(struct trace_array *tr)
@@ -914,6 +915,7 @@ ftrace_init_global_array_ops(struct trace_array *tr) { }
static inline void ftrace_reset_array_ops(struct trace_array *tr) { }
static inline void ftrace_init_tracefs(struct trace_array *tr, struct dentry *d) { }
static inline void ftrace_init_tracefs_toplevel(struct trace_array *tr, struct dentry *d) { }
+static inline void ftrace_clear_pids(struct trace_array *tr) { }
/* ftace_func_t type is not defined, use macro instead of static inline */
#define ftrace_init_array_ops(tr, func) do { } while (0)