On Thu, 13 Jun 2024 09:52:23 -0400 Steven Rostedt <[email protected]> wrote:
> From: "Steven Rostedt (Google)" <[email protected]> > > 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_b6...@mail.gmail.com/ > > Fixes: cc60ee813b503 ("function_graph: Use static_call and branch to optimize > entry function") > Reported-by: Naresh Kamboju <[email protected]> > Signed-off-by: Steven Rostedt (Google) <[email protected]> Looks good to me. Acked-by: Masami Hiramatsu (Google) <[email protected]> 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 > -- Masami Hiramatsu (Google) <[email protected]>
