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From: Walter Wu <walter-zh.wu@mediatek.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Randy Dunlap <rdunlap@infradead.org>, <akpm@linux-foundation.org>,
	<broonie@kernel.org>, <linux-fsdevel@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
	<linux-next@vger.kernel.org>, <mhocko@suse.cz>,
	<mm-commits@vger.kernel.org>, <sfr@canb.auug.org.au>,
	Josh Poimboeuf <jpoimboe@redhat.com>, <dvyukov@google.com>,
	Stephen Rothwell <sfr@canb.auug.org.au>
Subject: Re: mmotm 2020-03-03-22-28 uploaded (warning: objtool:)
Date: Thu, 5 Mar 2020 17:16:22 +0800	[thread overview]
Message-ID: <1583399782.17146.14.camel@mtksdccf07> (raw)
In-Reply-To: <20200305081842.GB2619@hirez.programming.kicks-ass.net>

On Thu, 2020-03-05 at 09:18 +0100, Peter Zijlstra wrote:
> On Thu, Mar 05, 2020 at 09:17:17AM +0100, Peter Zijlstra wrote:
> > On Wed, Mar 04, 2020 at 09:34:49AM -0800, Randy Dunlap wrote:
> 
> > > mm/kasan/common.o: warning: objtool: kasan_report()+0x13: call to report_enabled() with UACCESS enabled
> > 
> > I used next/master instead, and found the below broken commit
> > responsible for this.
> 
> > @@ -634,12 +637,20 @@ void kasan_free_shadow(const struct vm_struct *vm)
> >  #endif
> >  
> >  extern void __kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip);
> > +extern bool report_enabled(void);
> >  
> > -void kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip)
> > +bool kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip)
> >  {
> > -	unsigned long flags = user_access_save();
> > +	unsigned long flags;
> > +
> > +	if (likely(!report_enabled()))
> > +		return false;
> 
> This adds an explicit call before the user_access_save() and that is a
> straight on bug.
> 
Hi Peter,

Thanks for your help. Unfortunately, I don't reproduce it in our
environment, so I have asked Stephen, if I can reproduce it, then we
will send new patch.


Thanks.

Walter

> > +
> > +	flags = user_access_save();
> >  	__kasan_report(addr, size, is_write, ip);
> >  	user_access_restore(flags);
> > +
> > +	return true;
> >  }


  reply	other threads:[~2020-03-05  9:16 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-04  6:28 mmotm 2020-03-03-22-28 uploaded akpm
2020-03-04 17:10 ` mmotm 2020-03-03-22-28 uploaded (objtool warnings) Randy Dunlap
2020-03-04 17:34 ` mmotm 2020-03-03-22-28 uploaded (warning: objtool:) Randy Dunlap
2020-03-05  8:17   ` Peter Zijlstra
2020-03-05  8:18     ` Peter Zijlstra
2020-03-05  9:16       ` Walter Wu [this message]
2020-03-05  9:54         ` Peter Zijlstra
2020-03-05 17:04           ` Randy Dunlap
2020-03-11  1:30           ` Walter Wu
2020-03-11  1:33           ` Walter Wu

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