Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Fri, 16 Apr 2021 19:08:29 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
        Willy Tarreau <w@1wt.eu>,
        Wedson Almeida Filho <wedsonaf@google.com>,
        Miguel Ojeda <ojeda@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        rust-for-linux@vger.kernel.org,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        Linux Doc Mailing List <linux-doc@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 00/13] [RFC] Rust support
Message-ID: <20210416180829.GO2531743@casper.infradead.org>
References: <20210414184604.23473-1-ojeda@kernel.org>
 <YHlz54rd1YQHsOA/@hirez.programming.kicks-ass.net>
 <YHmMJWmzz2vZ3qQH@google.com>
 <YHmc2+bKQJ/XAATF@hirez.programming.kicks-ass.net>
 <YHmuX1NA5RF7C7XS@google.com>
 <20210416161444.GA10484@1wt.eu>
 <CANiq72nbkJFPmiJXX=L8PmkouKgKG1k-CxhZYpL1hcncYwa8JA@mail.gmail.com>
 <YHnG+GRwiMqgHGs5@hirez.programming.kicks-ass.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <YHnG+GRwiMqgHGs5@hirez.programming.kicks-ass.net>
Precedence: bulk

On Fri, Apr 16, 2021 at 07:18:48PM +0200, Peter Zijlstra wrote:
> On Fri, Apr 16, 2021 at 07:10:17PM +0200, Miguel Ojeda wrote:
> 
> > Of course, UB is only a subset of errors, but it is a major one, and
> > particularly critical for privileged code.
> 
> I've seen relatively few UBSAN warnings that weren't due to UBSAN being
> broken.

Lucky you.

84c34df158cf215b0cd1475ab3b8e6f212f81f23

(i'd argue this is C being broken; promoting only as far as int, when
assigning to an unsigned long is Bad, but until/unless either GCC fixes
that or the language committee realises that being stuck in the 1970s
is Bad, people are going to keep making this kind of mistake)