linux-kernel - Re: [PATCH net v5] bpf, net: Fix a potential race in do_sock

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Message-ID: <ZtKOAKlNalVLIz2E@mini-arch>
Date: Fri, 30 Aug 2024 20:29:04 -0700
From: Stanislav Fomichev <sdf@...ichev.me>
To: Tze-nan Wu <Tze-nan.Wu@...iatek.com>
Cc: netdev@...r.kernel.org, bpf@...r.kernel.org,
	Alexei Starovoitov <ast@...nel.org>, alexei.starovoitov@...il.com,
	bobule.chang@...iatek.com, wsd_upstream@...iatek.com,
	linux-kernel@...r.kernel.org, linux-mediatek@...ts.infradead.org,
	Kuniyuki Iwashima <kuniyu@...zon.com>, chen-yao.chang@...iatek.com,
	Yanghui Li <yanghui.li@...iatek.com>,
	Cheng-Jui Wang <cheng-jui.wang@...iatek.com>,
	Daniel Borkmann <daniel@...earbox.net>,
	John Fastabend <john.fastabend@...il.com>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>,
	KP Singh <kpsingh@...nel.org>, Hao Luo <haoluo@...gle.com>,
	Jiri Olsa <jolsa@...nel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH net v5] bpf, net: Fix a potential race in
 do_sock_getsockopt()

On 08/30, Tze-nan Wu wrote:
> There's a potential race when `cgroup_bpf_enabled(CGROUP_GETSOCKOPT)` is
> false during the execution of `BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN`, but
> becomes true when `BPF_CGROUP_RUN_PROG_GETSOCKOPT` is called.
> This inconsistency can lead to `BPF_CGROUP_RUN_PROG_GETSOCKOPT` receiving
> an "-EFAULT" from `__cgroup_bpf_run_filter_getsockopt(max_optlen=0)`.
> Scenario shown as below:
> 
>            `process A`                      `process B`
>            -----------                      ------------
>   BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN
>                                             enable CGROUP_GETSOCKOPT
>   BPF_CGROUP_RUN_PROG_GETSOCKOPT (-EFAULT)
> 
> To resolve this, remove the `BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN` macro and
> directly uses `copy_from_sockptr` to ensure that `max_optlen` is always 
> set before `BPF_CGROUP_RUN_PROG_GETSOCKOPT` is invoked.
> 
> Fixes: 0d01da6afc54 ("bpf: implement getsockopt and setsockopt hooks")
> Co-developed-by: Yanghui Li <yanghui.li@...iatek.com>
> Signed-off-by: Yanghui Li <yanghui.li@...iatek.com>
> Co-developed-by: Cheng-Jui Wang <cheng-jui.wang@...iatek.com>
> Signed-off-by: Cheng-Jui Wang <cheng-jui.wang@...iatek.com>
> Signed-off-by: Tze-nan Wu <Tze-nan.Wu@...iatek.com>

Acked-by: Stanislav Fomichev <sdf@...ichev.me>