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Fri, 23 Oct 2026 06:03:19 -0700 (PDT) Received: from toxicpanda.com ([153.61.196.242]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-67a3402fc9esm1223884d50.16.2026.10.23.06.03.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 23 Oct 2026 06:03:18 -0700 (PDT) Date: Fri, 23 Oct 2026 13:03:07 +0000 From: Josef Bacik To: "Serge Hallyn (AMD)" Cc: Christian Brauner , Paul Moore , linux-fsdevel@vger.kernel.org, linux-security-module@vger.kernel.org Subject: Re: [PATCH 01/13] cred: gather the rules for acting on a task by uid Message-ID: <20261023-cred-ids-reply-serge-5b0e9c47d21a@toxicpanda.com> In-Reply-To: References: <20261018-b4-cred-ids-v1-0-7bdf2db4ea9f@toxicpanda.com> <20261018-b4-cred-ids-v1-1-7bdf2db4ea9f@toxicpanda.com> X-Mailing-List: linux-security-module@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-Transfer-Encoding: 7bit On Fri, Oct 23, 2026 at 07:51:39AM -0500, Serge Hallyn (AMD) wrote: > Overall I like this, thanks. Thanks for taking a look. > > + default: > > + return false; > > What do you think about putting a BUG HERE? It's not actually > your intent for this ever to be called with 'which' not being > a valid value, right? Right, that's never supposed to happen, the callers all pass one of the three by name. I'd rather not BUG() though. It fails closed as it is, so the worst a bogus value does is get somebody an EPERM, which isn't worth taking the box down for. I agree it shouldn't be silent. I think VFS_WARN_ON_ONCE() fits, it's a WARN_ON_ONCE() with CONFIG_DEBUG_VFS and compiles away to nothing without it, so whoever adds a fourth value and forgets the switch hears about it in testing and nobody else pays for it. It's in use outside of fs/ already, kernel/nstree.c and kernel/nscommon.c have it. Christian, if that's fine with you could you fold the below into patch 1? Nothing later in the series touches kernel/cred.c so it shouldn't conflict with anything. Or I can send a v2, whichever is easier. Thanks, Josef diff --git a/kernel/cred.c b/kernel/cred.c index c067ef72b563..9a3ea6a1b96a 100644 --- a/kernel/cred.c +++ b/kernel/cred.c @@ -19,6 +19,7 @@ #include #include #include +#include #if 0 #define kdebug(FMT, ...) \ @@ -692,6 +693,7 @@ bool cred_ids_allow_control(const struct cred *subj, enum cred_ids which, gid = subj->fsgid; break; default: + VFS_WARN_ON_ONCE(1); return false; }