Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:18 as permitted sender) client-ip=2620:137:e000::1:18;
Date:   Fri, 25 Feb 2022 15:45:18 -0800
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Kees Cook <keescook@chromium.org>
Cc:     llvm@lists.linux.dev, Marco Elver <elver@google.com>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Vlastimil Babka <vbabka@suse.cz>, linux-mm@kvack.org,
        stable@vger.kernel.org,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Christoph Lameter <cl@linux.com>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Daniel Micay <danielmicay@gmail.com>,
        linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH] mm: Handle ksize() vs __alloc_size by forgetting size
Message-Id: <20220225154518.0d1159fdc6f37ee38e39e90c@linux-foundation.org>
In-Reply-To: <20220225221625.3531852-1-keescook@chromium.org>
References: <20220225221625.3531852-1-keescook@chromium.org>
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Precedence: bulk

On Fri, 25 Feb 2022 14:16:25 -0800 Kees Cook <keescook@chromium.org> wrote:

> If ksize() is used on an allocation, the compiler cannot make any
> assumptions about its size any more (as hinted by __alloc_size). Force
> it to forget.
> 
> One caller was using a container_of() construction that needed to be
> worked around.

Please, when fixing something do fully explain what that thing is.  I,
for one, simply cannot understand why this change is being proposed.

Especially when proposing a -stable backport!  Tell readers what was
the end-user impact of the bug.

> Link: https://github.com/ClangBuiltLinux/linux/issues/1599

Even that didn't tell me.  Is it just a clang warning?  Does the kernel
post your private keys on reddit then scribble all over your disk
drive?  I dunno.