Re: [PATCH bpf-next v1 3/8] bpf: Introduce load-acquire and store-release instructions

[Peilin Ye <yepeilin@google.com>]

On Tue, Jan 28, 2025 at 05:30:19PM -0800, Eduard Zingerman wrote:
> On Sat, 2025-01-25 at 02:18 +0000, Peilin Ye wrote:
> > +static int check_atomic_store(struct bpf_verifier_env *env, int insn_idx,
> > +			      struct bpf_insn *insn)
> > +{
> > +	int err;
> > +
> > +	err = check_reg_arg(env, insn->src_reg, SRC_OP);
> > +	if (err)
> > +		return err;
> > +
> > +	err = check_reg_arg(env, insn->dst_reg, SRC_OP);
> > +	if (err)
> > +		return err;
> > +
> > +	if (is_pointer_value(env, insn->src_reg)) {
> > +		verbose(env, "R%d leaks addr into mem\n", insn->src_reg);
> > +		return -EACCES;
> > +	}
> 
> Nit: this check is done by check_mem_access(), albeit only for
>      PTR_TO_MEM, I think it's better to be consistent with
>      what happens for regular stores and avoid this check here.

Got it.  Unprivileged programs will be able to store-release pointers to
the stack, then.  I'll update selftests accordingly.

Thanks,
Peilin Ye