linux-kernel - Re: [PATCH] KEYS: replace -EEXIST with -EBUSY

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Message-ID: <1793804.1767607035@warthog.procyon.org.uk>
Date: Mon, 05 Jan 2026 09:57:15 +0000
From: David Howells <dhowells@...hat.com>
To: Daniel Gomez <da.gomez@...nel.org>
Cc: dhowells@...hat.com, Lukas Wunner <lukas@...ner.de>,
    Ignat Korchagin <ignat@...udflare.com>,
    Herbert Xu <herbert@...dor.apana.org.au>,
    "David S. Miller" <davem@...emloft.net>,
    Jarkko Sakkinen <jarkko@...nel.org>,
    Paul Moore <paul@...l-moore.com>, James Morris <jmorris@...ei.org>,
    "Serge E.
 Hallyn" <serge@...lyn.com>,
    Luis Chamberlain <mcgrof@...nel.org>,
    Petr Pavlu <petr.pavlu@...e.com>,
    Sami Tolvanen <samitolvanen@...gle.com>,
    Aaron Tomlin <atomlin@...mlin.com>,
    Lucas De Marchi <demarchi@...nel.org>, keyrings@...r.kernel.org,
    linux-crypto@...r.kernel.org, linux-modules@...r.kernel.org,
    linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org,
    Daniel Gomez <da.gomez@...sung.com>
Subject: Re: [PATCH] KEYS: replace -EEXIST with -EBUSY

Daniel Gomez <da.gomez@...nel.org> wrote:

> From: Daniel Gomez <da.gomez@...sung.com>
> 
> The -EEXIST error code is reserved by the module loading infrastructure
> to indicate that a module is already loaded.

EEXIST means a file exists when you're trying to create it.  Granted we abuse
that somewhat rather than add ever more error codes, but you cannot reserve it
for indicating that a module exists.

> When a module's init
> function returns -EEXIST, userspace tools like kmod interpret this as
> "module already loaded" and treat the operation as successful, returning
> 0 to the user even though the module initialization actually failed.
> 
> This follows the precedent set by commit 54416fd76770 ("netfilter:
> conntrack: helper: Replace -EEXIST by -EBUSY") which fixed the same
> issue in nf_conntrack_helper_register().
> 
> Affected modules:
>   * pkcs8_key_parser x509_key_parser asymmetric_keys dns_resolver
>   * nvme_keyring pkcs7_test_key rxrpc turris_signing_key
> 
> Signed-off-by: Daniel Gomez <da.gomez@...sung.com>

Please don't.  Userspace can always check /proc/modules (assuming procfs is
enabled, I suppose).

David