Re: [PATCH] bpf: crypto: replace -EEXIST with -EBUSY

[Vadim Fedorenko]

On 20/12/2025 03:48, Daniel Gomez wrote:
> From: Daniel Gomez <da.gomez@xxxxxxxxxxx>
>
> The -EEXIST error code is reserved by the module loading infrastructure
> to indicate that a module is already loaded. 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().
>
> This affects bpf_crypto_skcipher module. While the configuration
> required to build it as a module is unlikely in practice, it is
> technically possible, so fix it for correctness.
>
> Signed-off-by: Daniel Gomez <da.gomez@xxxxxxxxxxx>
> ---
> The error code -EEXIST is reserved by the kernel module loader to
> indicate that a module with the same name is already loaded. When a
> module's init function returns -EEXIST, kmod interprets this as "module
> already loaded" and reports success instead of failure [1].
>
> The kernel module loader will include a safety net that provides -EEXIST
> to -EBUSY with a warning [2], and a documentation patch has been sent to
> prevent future occurrences [3].
>
> These affected code paths were identified using a static analysis tool
> [4] that traces -EEXIST returns to module_init(). The tool was developed
> with AI assistance and all findings were manually validated.
>
> Link: https://lore.kernel.org/all/aKEVQhJpRdiZSliu@xxxxxxxxxxxxx/ [1]
> Link: https://lore.kernel.org/all/20251013-module-warn-ret-v1-0-ab65b41af01f@xxxxxxxxx/ [2]
> Link: https://lore.kernel.org/all/20251218-dev-module-init-eexists-modules-docs-v1-0-361569aa782a@xxxxxxxxxxx/ [3]
> Link: https://gitlab.com/-/snippets/4913469 [4]

Even though I'm not quite sure that we should care once the core
module loader can adjust the error, the change looks ok to me:

Acked-by: Vadim Fedorenko <vadim.fedorenko@xxxxxxxxx>