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Tue, 3 Jun 2025 23:07:30 +0200 (CEST) From: Luis Gerhorst To: Kumar Kartikeya Dwivedi Cc: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Puranjay Mohan , Xu Kuohai , Catalin Marinas , Will Deacon , Hari Bathini , Christophe Leroy , Naveen N Rao , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Mykola Lysenko , Shuah Khan , Henriette Herzog , Saket Kumar Bhaskar , Cupertino Miranda , Jiayuan Chen , Matan Shachnai , Dimitar Kanaliev , Shung-Hsi Yu , Daniel Xu , bpf@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kselftest@vger.kernel.org, Maximilian Ott , Milan Stephan Subject: Re: [PATCH bpf-next v3 10/11] bpf: Allow nospec-protected var-offset stack access In-Reply-To: (Kumar Kartikeya Dwivedi's message of "Fri, 2 May 2025 02:03:12 +0200") References: <20250501073603.1402960-1-luis.gerhorst@fau.de> <20250501073603.1402960-11-luis.gerhorst@fau.de> User-Agent: mu4e 1.12.8; emacs 30.1 Date: Tue, 03 Jun 2025 23:07:30 +0200 Message-ID: <874iwwlejx.fsf@fau.de> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Type: text/plain Kumar Kartikeya Dwivedi writes: > Hmm, while reading related code, I noticed that sanitize_check_bounds > returns 0 in case the type is not map_value or stack. > It seems like it should be returning an error, cannot check right now > but I'm pretty sure these are not the two pointer types unprivileged > programs can access? > So smells like a bug? I now looked into this and as suspected it does not appear to be a bug but only misleading code, I have sent a patch with a detailed explanation and an assert: https://lore.kernel.org/bpf/20250603204557.332447-1-luis.gerhorst@fau.de/T/#u