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Message-ID: <a0da7702-dabe-49e4-87f4-5d6111f023a8@python.org> Date: Wed, 17 Jul 2024 09:26:22 +0100 From: Steve Dower <steve.dower@...hon.org> To: Jeff Xu <jeffxu@...gle.com>, Mickaël Salaün <mic@...ikod.net> Cc: Al Viro <viro@...iv.linux.org.uk>, Christian Brauner <brauner@...nel.org>, Kees Cook <keescook@...omium.org>, Linus Torvalds <torvalds@...ux-foundation.org>, Paul Moore <paul@...l-moore.com>, Theodore Ts'o <tytso@....edu>, Alejandro Colomar <alx.manpages@...il.com>, Aleksa Sarai <cyphar@...har.com>, Andrew Morton <akpm@...ux-foundation.org>, Andy Lutomirski <luto@...nel.org>, Arnd Bergmann <arnd@...db.de>, Casey Schaufler <casey@...aufler-ca.com>, Christian Heimes <christian@...hon.org>, Dmitry Vyukov <dvyukov@...gle.com>, Eric Biggers <ebiggers@...nel.org>, Eric Chiang <ericchiang@...gle.com>, Fan Wu <wufan@...ux.microsoft.com>, Florian Weimer <fweimer@...hat.com>, Geert Uytterhoeven <geert@...ux-m68k.org>, James Morris <jamorris@...ux.microsoft.com>, Jan Kara <jack@...e.cz>, Jann Horn <jannh@...gle.com>, Jonathan Corbet <corbet@....net>, Jordan R Abrahams <ajordanr@...gle.com>, Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>, Luca Boccassi <bluca@...ian.org>, Luis Chamberlain <mcgrof@...nel.org>, "Madhavan T . Venkataraman" <madvenka@...ux.microsoft.com>, Matt Bobrowski <mattbobrowski@...gle.com>, Matthew Garrett <mjg59@...f.ucam.org>, Matthew Wilcox <willy@...radead.org>, Miklos Szeredi <mszeredi@...hat.com>, Mimi Zohar <zohar@...ux.ibm.com>, Nicolas Bouchinet <nicolas.bouchinet@....gouv.fr>, Scott Shell <scottsh@...rosoft.com>, Shuah Khan <shuah@...nel.org>, Stephen Rothwell <sfr@...b.auug.org.au>, Steve Grubb <sgrubb@...hat.com>, Thibaut Sautereau <thibaut.sautereau@....gouv.fr>, Vincent Strubel <vincent.strubel@....gouv.fr>, Xiaoming Ni <nixiaoming@...wei.com>, Yin Fengwei <fengwei.yin@...el.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 v19 1/5] exec: Add a new AT_CHECK flag to execveat(2) On 17/07/2024 07:33, Jeff Xu wrote: > Consider those cases: I think: > a> relying purely on userspace for enforcement does't seem to be > effective, e.g. it is trivial to call open(), then mmap() it into > executable memory. If there's a way to do this without running executable code that had to pass a previous execveat() check, then yeah, it's not effective (e.g. a Python interpreter that *doesn't* enforce execveat() is a trivial way to do it). Once arbitrary code is running, all bets are off. So long as all arbitrary code is being checked itself, it's allowed to do things that would bypass later checks (and it's up to whoever audited it in the first place to prevent this by not giving it the special mark that allows it to pass the check). > b> if both user space and kernel need to call AT_CHECK, the faccessat > seems to be a better place for AT_CHECK, e.g. kernel can call > do_faccessat(AT_CHECK) and userspace can call faccessat(). This will > avoid complicating the execveat() code path. > > What do you think ? > > Thanks > -Jeff
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