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Message-ID: <Z5qpEkXq-X6ci9UU@google.com>
Date: Wed, 29 Jan 2025 22:17:54 +0000
From: Peilin Ye <yepeilin@...gle.com>
To: Eduard Zingerman <eddyz87@...il.com>
Cc: bpf@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, bpf@...f.org,
	Xu Kuohai <xukuohai@...weicloud.com>,
	David Vernet <void@...ifault.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu <song@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>,
	Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
	Jonathan Corbet <corbet@....net>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Puranjay Mohan <puranjay@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>, Quentin Monnet <qmo@...nel.org>,
	Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>,
	Josh Don <joshdon@...gle.com>, Barret Rhoden <brho@...gle.com>,
	Neel Natu <neelnatu@...gle.com>,
	Benjamin Segall <bsegall@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf-next v1 3/8] bpf: Introduce load-acquire and
 store-release instructions

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


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