Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Tue, 10 Sep 2019 01:59:30 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc:     20190819234111.9019-8-keescook@chromium.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Christophe Leroy <christophe.leroy@c-s.fr>,
        Peter Zijlstra <peterz@infradead.org>,
        Drew Davenport <ddavenport@chromium.org>,
        Arnd Bergmann <arnd@arndb.de>,
        "Steven Rostedt (VMware)" <rostedt@goodmis.org>,
        Feng Tang <feng.tang@intel.com>,
        Petr Mladek <pmladek@suse.com>,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
        Borislav Petkov <bp@suse.de>,
        YueHaibing <yuehaibing@huawei.com>, linux-arch@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 7/7] bug: Move WARN_ON() "cut here" into exception
 handler
Message-ID: <201909100157.CEE99802C@keescook>
References: <201908200943.601DD59DCE@keescook>
 <20190909160539.GA989@tigerII.localdomain>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20190909160539.GA989@tigerII.localdomain>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Tue, Sep 10, 2019 at 01:05:39AM +0900, Sergey Senozhatsky wrote:
> On (08/20/19 09:47), Kees Cook wrote:
> [..]
> > @@ -181,6 +181,15 @@ enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
> >  		}
> >  	}
> >  
> > +	/*
> > +	 * BUG() and WARN_ON() families don't print a custom debug message
> > +	 * before triggering the exception handler, so we must add the
> > +	 * "cut here" line now. WARN() issues its own "cut here" before the
> > +	 * extra debugging message it writes before triggering the handler.
> > +	 */
> > +	if ((bug->flags & BUGFLAG_NO_CUT_HERE) == 0)
> > +		printk(KERN_DEFAULT CUT_HERE);
> 
> Shouldn't this be pr_warn() or pr_crit()?

The pr_* helpers here would (potentially) add unwanted prefixes, so
those aren't used. KERN_DEFAULT is used here because that's how it's
always been printed. I didn't want to change that for this refactoring
work. I'm not opposed to it, generally speaking, though. :)

-- 
Kees Cook