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From: Alexander Potapenko <glider@google.com>
To: Peter Collingbourne <pcc@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>,
	George Popescu <georgepope@android.com>,
	 Elena Petrova <lenaptr@google.com>,
	Evgenii Stepanov <eugenis@google.com>,
	 Andrew Morton <akpm@linux-foundation.org>,
	 Linux Memory Management List <linux-mm@kvack.org>,
	stable@vger.kernel.org
Subject: Re: [PATCH v2] kasan: fix unit tests with CONFIG_UBSAN_LOCAL_BOUNDS enabled
Date: Fri, 7 May 2021 09:15:27 +0200	[thread overview]
Message-ID: <CAG_fn=V_5nvNT54gFROiHGTz11g_XMqoTWjRpomG01r56ZOP6Q@mail.gmail.com> (raw)
In-Reply-To: <20210507025915.1464056-1-pcc@google.com>

On Fri, May 7, 2021 at 4:59 AM Peter Collingbourne <pcc@google.com> wrote:
>
> These tests deliberately access these arrays out of bounds,
> which will cause the dynamic local bounds checks inserted by
> CONFIG_UBSAN_LOCAL_BOUNDS to fail and panic the kernel. To avoid this
> problem, access the arrays via volatile pointers, which will prevent
> the compiler from being able to determine the array bounds.

Thanks for tracking this down! These crashes have been puzzling me for a while.

> These accesses use volatile pointers to char (char *volatile) rather
> than the more conventional pointers to volatile char (volatile char *)
> because we want to prevent the compiler from making inferences about
> the pointer itself (i.e. its array bounds), not the data that it
> refers to.
>

> Signed-off-by: Peter Collingbourne <pcc@google.com>
Tested-by: Alexander Potapenko <glider@google.com>

(also note you are missing the Acked-by: here that Andrey gave)


  reply	other threads:[~2021-05-07  7:16 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-07  2:59 Peter Collingbourne
2021-05-07  7:15 ` Alexander Potapenko [this message]
2021-05-07 13:42 ` Andrey Konovalov

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