linux-kernel - Re: [PATCH v7 00/43] Add KernelMemorySanitizer infrastructure

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Message-Id: <20220915140748.843a2ebc2efb35f509b56ef4@linux-foundation.org>
Date:   Thu, 15 Sep 2022 14:07:48 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Alexander Potapenko <glider@...gle.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Christoph Hellwig <hch@....de>,
        Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Eric Biggers <ebiggers@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Ilya Leoshkevich <iii@...ux.ibm.com>,
        Ingo Molnar <mingo@...hat.com>, Jens Axboe <axboe@...nel.dk>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Kees Cook <keescook@...omium.org>,
        Marco Elver <elver@...gle.com>,
        Mark Rutland <mark.rutland@....com>,
        Matthew Wilcox <willy@...radead.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Pekka Enberg <penberg@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Petr Mladek <pmladek@...e.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Vegard Nossum <vegard.nossum@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>, kasan-dev@...glegroups.com,
        linux-mm@...ck.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 00/43] Add KernelMemorySanitizer infrastructure

On Thu, 15 Sep 2022 14:05:51 -0700 Andrew Morton <akpm@...ux-foundation.org> wrote:

> 
> For "kmsan: add KMSAN runtime core":
> 
> ...
>
> @@ -219,23 +212,22 @@ depot_stack_handle_t kmsan_internal_chai
>  	 * Make sure we have enough spare bits in @id to hold the UAF bit and
>  	 * the chain depth.
>  	 */
> -	BUILD_BUG_ON((1 << STACK_DEPOT_EXTRA_BITS) <= (MAX_CHAIN_DEPTH << 1));
> +	BUILD_BUG_ON(
> +		(1 << STACK_DEPOT_EXTRA_BITS) <= (KMSAN_MAX_ORIGIN_DEPTH << 1));
>  
>  	extra_bits = stack_depot_get_extra_bits(id);
>  	depth = kmsan_depth_from_eb(extra_bits);
>  	uaf = kmsan_uaf_from_eb(extra_bits);
>  
> -	if (depth >= MAX_CHAIN_DEPTH) {
> -		static atomic_long_t kmsan_skipped_origins;
> -		long skipped = atomic_long_inc_return(&kmsan_skipped_origins);
> -
> -		if (skipped % NUM_SKIPPED_TO_WARN == 0) {
> -			pr_warn("not chained %ld origins\n", skipped);
> -			dump_stack();
> -			kmsan_print_origin(id);
> -		}

Wouldn't it be neat if printk_ratelimited() returned true if it printed
something.

But you deleted this user of that neatness anyway ;)