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Date:   Wed, 30 Mar 2022 10:46:15 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Alexander Potapenko <glider@google.com>
Cc:     Alexander Viro <viro@zeniv.linux.org.uk>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andrey Konovalov <andreyknvl@google.com>,
        Andy Lutomirski <luto@kernel.org>,
        Arnd Bergmann <arnd@arndb.de>, Borislav Petkov <bp@alien8.de>,
        Christoph Hellwig <hch@lst.de>,
        Christoph Lameter <cl@linux.com>,
        David Rientjes <rientjes@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Eric Dumazet <edumazet@google.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Ilya Leoshkevich <iii@linux.ibm.com>,
        Ingo Molnar <mingo@redhat.com>, Jens Axboe <axboe@kernel.dk>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Kees Cook <keescook@chromium.org>,
        Marco Elver <elver@google.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Matthew Wilcox <willy@infradead.org>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Pekka Enberg <penberg@kernel.org>,
        Petr Mladek <pmladek@suse.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Vegard Nossum <vegard.nossum@oracle.com>,
        Vlastimil Babka <vbabka@suse.cz>, linux-mm@kvack.org,
        linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 38/48] objtool: kmsan: list KMSAN API functions as
 uaccess-safe
Message-ID: <20220330084615.GH8939@worktop.programming.kicks-ass.net>
References: <20220329124017.737571-1-glider@google.com>
 <20220329124017.737571-39-glider@google.com>
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In-Reply-To: <20220329124017.737571-39-glider@google.com>
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On Tue, Mar 29, 2022 at 02:40:07PM +0200, Alexander Potapenko wrote:
> KMSAN inserts API function calls in a lot of places (function entries
> and exits, local variables, memory accesses), so they may get called
> from the uaccess regions as well.

That's insufficient. Explain how you did the right thing and made these
functions actually safe to be called in this context.

> Signed-off-by: Alexander Potapenko <glider@google.com>
> ---
> Link: https://linux-review.googlesource.com/id/I242bc9816273fecad4ea3d977393784396bb3c35
> ---
>  tools/objtool/check.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/tools/objtool/check.c b/tools/objtool/check.c
> index 7c33ec67c4a95..8518eaf05bff0 100644
> --- a/tools/objtool/check.c
> +++ b/tools/objtool/check.c
> @@ -943,6 +943,25 @@ static const char *uaccess_safe_builtin[] = {
>  	"__sanitizer_cov_trace_cmp4",
>  	"__sanitizer_cov_trace_cmp8",
>  	"__sanitizer_cov_trace_switch",
> +	/* KMSAN */
> +	"kmsan_copy_to_user",
> +	"kmsan_report",
> +	"kmsan_unpoison_memory",
> +	"__msan_chain_origin",
> +	"__msan_get_context_state",
> +	"__msan_instrument_asm_store",
> +	"__msan_metadata_ptr_for_load_1",
> +	"__msan_metadata_ptr_for_load_2",
> +	"__msan_metadata_ptr_for_load_4",
> +	"__msan_metadata_ptr_for_load_8",
> +	"__msan_metadata_ptr_for_load_n",
> +	"__msan_metadata_ptr_for_store_1",
> +	"__msan_metadata_ptr_for_store_2",
> +	"__msan_metadata_ptr_for_store_4",
> +	"__msan_metadata_ptr_for_store_8",
> +	"__msan_metadata_ptr_for_store_n",
> +	"__msan_poison_alloca",
> +	"__msan_warning",
>  	/* UBSAN */
>  	"ubsan_type_mismatch_common",
>  	"__ubsan_handle_type_mismatch",
> -- 
> 2.35.1.1021.g381101b075-goog
>