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

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Message-ID: <CAADnVQJAmb8NFWFCgpBUO9wT3NTzTJAd2gH1cs3rpLxAK1WNrQ@mail.gmail.com>
Date: Tue, 23 Dec 2025 09:23:57 -1000
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
Cc: Daniel Gomez <da.gomez@...nel.org>, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, 
	Martin KaFai Lau <martin.lau@...ux.dev>, Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, 
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, 
	Jiri Olsa <jolsa@...nel.org>, 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>, bpf <bpf@...r.kernel.org>, linux-modules@...r.kernel.org, 
	LKML <linux-kernel@...r.kernel.org>, Daniel Gomez <da.gomez@...sung.com>
Subject: Re: [PATCH] bpf: crypto: replace -EEXIST with -EBUSY

On Sat, Dec 20, 2025 at 8:55 AM Vadim Fedorenko
<vadim.fedorenko@...ux.dev> wrote:
>
> On 20/12/2025 03:48, Daniel Gomez 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. 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@...sung.com>
> > ---
> > 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@orbyte.nwl.cc/ [1]
> > Link: https://lore.kernel.org/all/20251013-module-warn-ret-v1-0-ab65b41af01f@intel.com/ [2]
> > Link: https://lore.kernel.org/all/20251218-dev-module-init-eexists-modules-docs-v1-0-361569aa782a@samsung.com/ [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@...ux.dev>

Applied to bpf-next.