Messages in this thread Patch in this message | | | Date | Mon, 17 Apr 2017 20:52:44 +0900 | From | Masami Hiramatsu <> | Subject | Re: [PATCH 1/4] ftrace: Fix function pid filter on instances |
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On Mon, 17 Apr 2017 11:44:27 +0900 Namhyung Kim <namhyung@kernel.org> wrote:
> 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_pid_reset() to unregister the probe. As ^^^^^^^^^^^^^^^^ ftrace_clear_pids()?
> instance_rmdir() already updated ftrace codes, it can just free the > filter safely.
And following explanation may not need.
The code looks good to me.
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Thanks,
> > Fixes: 0c8916c34203 ("tracing: Add rmdir to remove multibuffer instances") > Signed-off-by: Namhyung Kim <namhyung@kernel.org> > --- > kernel/trace/ftrace.c | 9 +++++++++ > kernel/trace/trace.c | 1 + > kernel/trace/trace.h | 2 ++ > 3 files changed, 12 insertions(+) > > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c > index 34f63e78d661..7b27066c5ed0 100644 > --- a/kernel/trace/ftrace.c > +++ b/kernel/trace/ftrace.c > @@ -5610,6 +5610,15 @@ static void clear_ftrace_pids(struct trace_array *tr) > trace_free_pid_list(pid_list); > } > > +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) > { > mutex_lock(&ftrace_lock); > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index b5d4b80f2d45..0bf623c182da 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -7485,6 +7485,7 @@ static int instance_rmdir(const char *name) > > tracing_set_nop(tr); > event_trace_del_tracer(tr); > + ftrace_clear_pids(tr); > ftrace_destroy_function_files(tr); > tracefs_remove_recursive(tr->dir); > free_trace_buffers(tr); > diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h > index 571acee52a32..ee27163b7549 100644 > --- a/kernel/trace/trace.h > +++ b/kernel/trace/trace.h > @@ -897,6 +897,7 @@ 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); > int init_function_trace(void); > +void ftrace_clear_pids(struct trace_array *tr); > #else > static inline int ftrace_trace_task(struct trace_array *tr) > { > @@ -916,6 +917,7 @@ 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 int init_function_trace(void) { return 0; } > +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) > #endif /* CONFIG_FUNCTION_TRACER */ > -- > 2.12.2 >
-- Masami Hiramatsu <mhiramat@kernel.org>
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