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Thu, 29 Oct 2026 10:15:55 -0700 (PDT) Received: from localhost ([116.86.153.182]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3ae85e567ecsm64167a91.3.2026.10.29.10.15.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 Oct 2026 10:15:54 -0700 (PDT) Date: Fri, 30 Oct 2026 01:15:51 +0800 From: Chris Down To: Alexei Starovoitov Cc: Nuoqi Gui , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Martin KaFai Lau , Mykyta Yatsenko , Shuah Khan , bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH bpf 0/2] bpf: Gate dynptr probe-read kfuncs like helpers Message-ID: References: <20260615-f01-07-dynptr-probe-read-cap-v1-0-e626cd61a381@mails.tsinghua.edu.cn> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/2.3.3 (9073d26d) (2026-06-12) Hey Alexei, Alexei Starovoitov writes: > It's fine as-is. Won't fix. Could you expand a bit on the lockdown side of this? I ran into the same discrepancy independently and was preparing fixes until I found this thread while looking for prior discussion. The CAP_PERFMON side is now covered by 81c975aae375 ("bpf: Require CAP_PERFMON for kfuncs reading memory"), but the probe_read_kernel helpers still check LOCKDOWN_BPF_READ_KERNEL while the matching dynptr kfuncs don't. Is that intentional? I also checked bpf_rdonly_cast() plus typed loads, which can still read kernel memory in that mode, so I can see why just gating the two dynptr kfuncs wouldn't give us a consistent boundary. I'm less clear on whether that's the reason for leaving them alone or there's some other reason. Thanks, Chris