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AJvYcCWORQtd8BfPhbZhRtP+3WhDTmNoUUiGvjcD7S+t3mmA3Y8ixS5hz/L6XFlPrtypOWNj9Nev70qxhHeaNbxpuhPE0MnJ X-Gm-Message-State: AOJu0Yx+AZZlZa2hANMG8UsAJA4foAzTuwvjGhy+TUEvGWiCG0Q5i1IT Ye05PF01d8SHdFaCZzcziKCvYImOmA7e+5YcCVCW4DjYycGd5WL+76mPJbUDbvs= X-Google-Smtp-Source: AGHT+IGmFzRBxjkHf31z6d3Lq36FFy7Enc6jBbimLiq65p2x3hU5JphLJecADC001IRmMLuW5xDSbw== X-Received: by 2002:a17:906:3b09:b0:a46:ba19:2e99 with SMTP id g9-20020a1709063b0900b00a46ba192e99mr4763483ejf.26.1711374733929; Mon, 25 Mar 2024 06:52:13 -0700 (PDT) Received: from cloudflare.com ([2a09:bac5:5064:2dc::49:1a6]) by smtp.gmail.com with ESMTPSA id i15-20020a170906090f00b00a46d9966ff8sm3114614ejd.147.2024.03.25.06.52.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 25 Mar 2024 06:52:13 -0700 (PDT) References: <000000000000dc9aca0613ec855c@google.com> <87y1a6biie.fsf@cloudflare.com> User-agent: mu4e 1.6.10; emacs 29.2 From: Jakub Sitnicki To: Alexei Starovoitov , Edward Adam Davis , John Fastabend Cc: syzbot+c4f4d25859c2e5859988@syzkaller.appspotmail.com, 42.hyeyoo@gmail.com, andrii@kernel.org, ast@kernel.org, bpf@vger.kernel.org, daniel@iogearbox.net, davem@davemloft.net, edumazet@google.com, kafai@fb.com, kpsingh@kernel.org, kuba@kernel.org, linux-kernel@vger.kernel.org, namhyung@kernel.org, netdev@vger.kernel.org, pabeni@redhat.com, peterz@infradead.org, songliubraving@fb.com, syzkaller-bugs@googlegroups.com, yhs@fb.com Subject: Re: [PATCH] bpf, sockmap: fix deadlock in rcu_report_exp_cpu_mult Date: Mon, 25 Mar 2024 14:49:19 +0100 In-reply-to: <87y1a6biie.fsf@cloudflare.com> Message-ID: <87ttkuber7.fsf@cloudflare.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain On Mon, Mar 25, 2024 at 01:23 PM +01, Jakub Sitnicki wrote: [...] > But we also need to cover sock_map_unref->sock_sock_map_del_link called > from sock_hash_delete_elem. It also grabs a spin lock. On second look, no need to disable interrupts in sock_map_unref->sock_sock_map_del_link. Call is enclosed in the critical section in sock_hash_delete_elem that has been updated. I have a question, though, why are we patching sock_hash_free? It doesn't get called unless there are no more existing users of the BPF map. So nothing can mutate it from interrupt context. [...]