linux-kernel - Re: [PATCH bpf] bpf: cpumap: Fix memory leak in cpu_map_update

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Date:   Tue, 11 Jul 2023 18:06:34 +0200
From:   Jesper Dangaard Brouer <jbrouer@...hat.com>
To:     Pu Lehui <pulehui@...weicloud.com>, bpf@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     brouer@...hat.com, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        Xu Kuohai <xukuohai@...wei.com>, Pu Lehui <pulehui@...wei.com>
Subject: Re: [PATCH bpf] bpf: cpumap: Fix memory leak in cpu_map_update_elem


On 11/07/2023 13.58, Pu Lehui wrote:
> From: Pu Lehui <pulehui@...wei.com>
> 
> Syzkaller reported a memory leak as follows:
> 
[...]>
> In the cpu_map_update_elem flow, when kthread_stop is called before
> calling the threadfn of rcpu->kthread, since the KTHREAD_SHOULD_STOP bit
> of kthread has been set by kthread_stop, the threadfn of rcpu->kthread
> will never be executed, and rcpu->refcnt will never be 0, which will
> lead to the allocated rcpu, rcpu->queue and rcpu->queue->queue cannot be
> released.
> 
> Calling kthread_stop before executing kthread's threadfn will return
> -EINTR. We can complete the release of memory resources in this state.
> 
> Fixes: 6710e1126934 ("bpf: introduce new bpf cpu map type BPF_MAP_TYPE_CPUMAP")
> Signed-off-by: Pu Lehui <pulehui@...wei.com>

LGTM, thanks for fixing this.

Acked-by: Jesper Dangaard Brouer <hawk@...nel.org>