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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Thu, 1 Dec 2022 13:13:35 -0800
Message-ID: <CAHk-=wjeq1m=9mU17WzfRQ1W6N0SgKHY-e2J35SpppWwUUBFbQ@mail.gmail.com>
Subject: Re: [PATCH] error-injection: Add prompt for function error injection
To:     Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Chris Mason <clm@meta.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Borislav Petkov <bp@alien8.de>,
        LKML <linux-kernel@vger.kernel.org>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Kees Cook <keescook@chromium.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        KP Singh <kpsingh@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Florent Revest <revest@chromium.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Christoph Hellwig <hch@infradead.org>,
        Benjamin Tissoires <benjamin.tissoires@redhat.com>
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On Thu, Dec 1, 2022 at 8:59 AM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> The hid-bpf framework depends on it.

Ok, this is completely unacceptably disgusting hack.

That needs fixing.

> Either hid-bpf or bpf core can add
> "depends on FUNCTION_ERROR_INJECTION"

No, it needs to be narrowed down a lot. Nobody sane wants error
injection just because they want some random HID thing.

And no, BPF shouldn't need it either.

This needs to be narrowed down to the point where HID can say "I want
*this* particular call to be able to be a bpf call.

Stop this crazy "bpf / hid needs error injection" when that then
implies a _lot_ more than that, plus is documented to be something
entirely different anyway.

I realize that HID has mis-used the "we could just use error injection
here to instead insert random bpf code", but that's a complete hack.

Plus it seems to happily not even have made it into mainline anyway,
and only exists in linux-next. Let's head that disgusting hack off at
the pass.

I'm going to apply Steven's patch, because honestly, we need to fix
this disgusting mess *before* it gets to mainline, rather than say
"oh, we already have broken users in next, so let's bend over
backwards for that".

The code is called "error injection", not "random bpf extension"

               Linus