| Message ID | 20240613095223.1f07e3a4@rorschach.local.home (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 63a8dfb889112ab4a065aa60a9a1b590b410d055 |
| Headers | show |
| Series | function_graph: Add READ_ONCE() when accessing fgraph_array[] | expand |
On Thu, 13 Jun 2024 09:52:23 -0400 Steven Rostedt <rostedt@goodmis.org> wrote: > From: "Steven Rostedt (Google)" <rostedt@goodmis.org> > > In function_graph_enter() there's a loop that looks at fgraph_array[] > elements which are fgraph_ops. It first tests if it is a fgraph_stub op, > and if so skips it, as that's just there as a place holder. Then it checks > the fgraph_ops filters to see if the ops wants to trace the current > function. > > But if the compiler reloads the fgraph_array[] after the check against > fgraph_stub, it could race with the fgraph_array[] being updated with the > fgraph_stub. That would cause the stub to be processed. But the stub has a > null "func_hash" field which will cause a NULL pointer dereference. > > Add a READ_ONCE() so that the gops that is compared against the > fgraph_stub is also the gops that is processed later. > > Link: https://lore.kernel.org/all/CA+G9fYsSVJQZH=nM=1cjTc94PgSnMF9y65BnOv6XSoCG_b6wmw@mail.gmail.com/ > > Fixes: cc60ee813b503 ("function_graph: Use static_call and branch to optimize entry function") > Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org> > Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> Looks good to me. Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Thanks. > --- > kernel/trace/fgraph.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c > index 8317d1a7f43a..fc205ad167a9 100644 > --- a/kernel/trace/fgraph.c > +++ b/kernel/trace/fgraph.c > @@ -641,7 +641,7 @@ int function_graph_enter(unsigned long ret, unsigned long func, > { > for_each_set_bit(i, &fgraph_array_bitmask, > sizeof(fgraph_array_bitmask) * BITS_PER_BYTE) { > - struct fgraph_ops *gops = fgraph_array[i]; > + struct fgraph_ops *gops = READ_ONCE(fgraph_array[i]); > int save_curr_ret_stack; > > if (gops == &fgraph_stub) > -- > 2.43.0 >
diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c index 8317d1a7f43a..fc205ad167a9 100644 --- a/kernel/trace/fgraph.c +++ b/kernel/trace/fgraph.c @@ -641,7 +641,7 @@ int function_graph_enter(unsigned long ret, unsigned long func, { for_each_set_bit(i, &fgraph_array_bitmask, sizeof(fgraph_array_bitmask) * BITS_PER_BYTE) { - struct fgraph_ops *gops = fgraph_array[i]; + struct fgraph_ops *gops = READ_ONCE(fgraph_array[i]); int save_curr_ret_stack; if (gops == &fgraph_stub)