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Message-ID: <20250826123041.GB1603531@mit.edu> Date: Tue, 26 Aug 2025 08:30:41 -0400 From: "Theodore Ts'o" <tytso@....edu> To: Mickaël Salaün <mic@...ikod.net> Cc: Christian Brauner <brauner@...nel.org>, Al Viro <viro@...iv.linux.org.uk>, Kees Cook <keescook@...omium.org>, Paul Moore <paul@...l-moore.com>, Serge Hallyn <serge@...lyn.com>, Andy Lutomirski <luto@...nel.org>, Arnd Bergmann <arnd@...db.de>, Christian Heimes <christian@...hon.org>, Dmitry Vyukov <dvyukov@...gle.com>, Elliott Hughes <enh@...gle.com>, Fan Wu <wufan@...ux.microsoft.com>, Florian Weimer <fweimer@...hat.com>, Jann Horn <jannh@...gle.com>, Jeff Xu <jeffxu@...gle.com>, Jonathan Corbet <corbet@....net>, Jordan R Abrahams <ajordanr@...gle.com>, Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>, Luca Boccassi <bluca@...ian.org>, Matt Bobrowski <mattbobrowski@...gle.com>, Miklos Szeredi <mszeredi@...hat.com>, Mimi Zohar <zohar@...ux.ibm.com>, Nicolas Bouchinet <nicolas.bouchinet@....cyber.gouv.fr>, Robert Waite <rowait@...rosoft.com>, Roberto Sassu <roberto.sassu@...wei.com>, Scott Shell <scottsh@...rosoft.com>, Steve Dower <steve.dower@...hon.org>, Steve Grubb <sgrubb@...hat.com>, kernel-hardening@...ts.openwall.com, linux-api@...r.kernel.org, linux-fsdevel@...r.kernel.org, linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org Subject: Re: [RFC PATCH v1 0/2] Add O_DENY_WRITE (complement AT_EXECVE_CHECK) Is there a single, unified design and requirements document that describes the threat model, and what you are trying to achieve with AT_EXECVE_CHECK and O_DENY_WRITE? I've been looking at the cover letters for AT_EXECVE_CHECK and O_DENY_WRITE, and the documentation that has landed for AT_EXECVE_CHECK and it really doesn't describe what *are* the checks that AT_EXECVE_CHECK is trying to achieve: "The AT_EXECVE_CHECK execveat(2) flag, and the SECBIT_EXEC_RESTRICT_FILE and SECBIT_EXEC_DENY_INTERACTIVE securebits are intended for script interpreters and dynamic linkers to enforce a consistent execution security policy handled by the kernel." Um, what security policy? What checks? What is a sample exploit which is blocked by AT_EXECVE_CHECK? And then on top of it, why can't you do these checks by modifying the script interpreters? Confused, - Ted
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