ftrace: Fix function pid filter on instances
commitd879d0b8c1
upstream. 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:0c8916c342
("tracing: Add rmdir to remove multibuffer instances") Cc: Ingo Molnar <mingo@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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -5401,6 +5401,15 @@ static void clear_ftrace_pids(struct trace_array *tr)
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trace_free_pid_list(pid_list);
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}
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void ftrace_clear_pids(struct trace_array *tr)
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{
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mutex_lock(&ftrace_lock);
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clear_ftrace_pids(tr);
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mutex_unlock(&ftrace_lock);
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}
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static void ftrace_pid_reset(struct trace_array *tr)
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{
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mutex_lock(&ftrace_lock);
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@ -7150,6 +7150,7 @@ static int instance_rmdir(const char *name)
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tracing_set_nop(tr);
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event_trace_del_tracer(tr);
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ftrace_clear_pids(tr);
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ftrace_destroy_function_files(tr);
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tracefs_remove_recursive(tr->dir);
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free_trace_buffers(tr);
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@ -870,6 +870,7 @@ int using_ftrace_ops_list_func(void);
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void ftrace_init_tracefs(struct trace_array *tr, struct dentry *d_tracer);
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void ftrace_init_tracefs_toplevel(struct trace_array *tr,
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struct dentry *d_tracer);
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void ftrace_clear_pids(struct trace_array *tr);
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#else
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static inline int ftrace_trace_task(struct trace_array *tr)
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{
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@ -888,6 +889,7 @@ ftrace_init_global_array_ops(struct trace_array *tr) { }
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static inline void ftrace_reset_array_ops(struct trace_array *tr) { }
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static inline void ftrace_init_tracefs(struct trace_array *tr, struct dentry *d) { }
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static inline void ftrace_init_tracefs_toplevel(struct trace_array *tr, struct dentry *d) { }
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static inline void ftrace_clear_pids(struct trace_array *tr) { }
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/* ftace_func_t type is not defined, use macro instead of static inline */
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#define ftrace_init_array_ops(tr, func) do { } while (0)
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#endif /* CONFIG_FUNCTION_TRACER */
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