From: Peter Zijlstra <peterz@infradead.org>
To: Walter Wu <walter-zh.wu@mediatek.com>
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
Subject: Re: mmotm 2020-03-03-22-28 uploaded (warning: objtool:)
Date: Thu, 5 Mar 2020 10:54:36 +0100 [thread overview]
Message-ID: <20200305095436.GV2596@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <1583399782.17146.14.camel@mtksdccf07>
On Thu, Mar 05, 2020 at 05:16:22PM +0800, Walter Wu wrote:
> 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.
The patch is trivial; and all you need is an x86_64 (cross) compiler to
reproduce.
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index ad2dc0c9cc17..2906358e42f0 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -618,16 +618,17 @@ extern bool report_enabled(void);
bool kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip)
{
- unsigned long flags;
+ unsigned long flags = user_access_save();
+ bool ret = false;
- if (likely(!report_enabled()))
- return false;
+ if (likely(report_enabled())) {
+ __kasan_report(addr, size, is_write, ip);
+ ret = true;
+ }
- flags = user_access_save();
- __kasan_report(addr, size, is_write, ip);
user_access_restore(flags);
- return true;
+ return ret;
}
#ifdef CONFIG_MEMORY_HOTPLUG
next prev parent reply other threads:[~2020-03-05 9:54 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
2020-03-05 9:54 ` Peter Zijlstra [this message]
2020-03-05 17:04 ` Randy Dunlap
2020-03-11 1:30 ` Walter Wu
2020-03-11 1:33 ` Walter Wu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200305095436.GV2596@hirez.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=akpm@linux-foundation.org \
--cc=broonie@kernel.org \
--cc=dvyukov@google.com \
--cc=jpoimboe@redhat.com \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-next@vger.kernel.org \
--cc=mhocko@suse.cz \
--cc=mm-commits@vger.kernel.org \
--cc=rdunlap@infradead.org \
--cc=sfr@canb.auug.org.au \
--cc=walter-zh.wu@mediatek.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).