linux-kernel - Re: [PATCH v7 18/43] instrumented.h: add KMSAN support

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Message-ID: <Y1BXQlu+JOoJi6Yk@elver.google.com>
Date:   Wed, 19 Oct 2022 22:00:02 +0200
From:   Marco Elver <elver@...gle.com>
To:     youling 257 <youling257@...il.com>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Christoph Hellwig <hch@....de>,
        Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Eric Biggers <ebiggers@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Ilya Leoshkevich <iii@...ux.ibm.com>,
        Ingo Molnar <mingo@...hat.com>, Jens Axboe <axboe@...nel.dk>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Kees Cook <keescook@...omium.org>,
        Mark Rutland <mark.rutland@....com>,
        Matthew Wilcox <willy@...radead.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Pekka Enberg <penberg@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Petr Mladek <pmladek@...e.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Vegard Nossum <vegard.nossum@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>, kasan-dev@...glegroups.com,
        linux-mm@...ck.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 18/43] instrumented.h: add KMSAN support

On Thu, Oct 20, 2022 at 03:29AM +0800, youling 257 wrote:
[...]
> > What arch?
> > If x86, can you try to revert only the change to
> > instrument_get_user()? (I wonder if the u64 conversion is causing
> > issues.)
> >
> arch x86, this's my revert,
> https://github.com/youling257/android-mainline/commit/401cbfa61cbfc20c87a5be8e2dda68ac5702389f
> i tried different revert, have to remove kmsan_copy_to_user.

There you reverted only instrument_put_user() - does it fix the issue?

If not, can you try only something like this (only revert
instrument_get_user()):

diff --git a/include/linux/instrumented.h b/include/linux/instrumented.h
index 501fa8486749..dbe3ec38d0e6 100644
--- a/include/linux/instrumented.h
+++ b/include/linux/instrumented.h
@@ -167,9 +167,6 @@ instrument_copy_from_user_after(const void *to, const void __user *from,
  */
 #define instrument_get_user(to)				\
 ({							\
-	u64 __tmp = (u64)(to);				\
-	kmsan_unpoison_memory(&__tmp, sizeof(__tmp));	\
-	to = __tmp;					\
 })
 

Once we know which one of these is the issue, we can figure out a proper
fix.

Thanks,

-- Marco