From: Marco Elver <elver@google.com>
To: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
Cc: Nicholas Tang <nicholas.tang@mediatek.com>,
Andrew Yang <andrew.yang@mediatek.com>,
Andrey Konovalov <andreyknvl@gmail.com>,
Andrey Ryabinin <ryabinin.a.a@gmail.com>,
Alexander Potapenko <glider@google.com>,
Chinwen Chang <chinwen.chang@mediatek.com>,
Andrew Morton <akpm@linux-foundation.org>,
kasan-dev@googlegroups.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-mediatek@lists.infradead.org,
Catalin Marinas <catalin.marinas@arm.com>
Subject: Re: [PATCH 1/2] kasan, mm: reset tag when access metadata
Date: Tue, 27 Jul 2021 09:10:51 +0200 [thread overview]
Message-ID: <CANpmjNM03Pag9OvBBVnWnSBePRxsT+BvZtBwrh_61Qzmvp+dvA@mail.gmail.com> (raw)
In-Reply-To: <20210727040021.21371-2-Kuan-Ying.Lee@mediatek.com>
+Cc Catalin
On Tue, 27 Jul 2021 at 06:00, Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com> wrote:
>
> Hardware tag-based KASAN doesn't use compiler instrumentation, we
> can not use kasan_disable_current() to ignore tag check.
>
> Thus, we need to reset tags when accessing metadata.
>
> Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
This looks reasonable, but the patch title is not saying this is
kmemleak, nor does the description say what the problem is. What
problem did you encounter? Was it a false positive?
Perhaps this should have been "kmemleak, kasan: reset pointer tags to
avoid false positives" ?
> ---
> mm/kmemleak.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/mm/kmemleak.c b/mm/kmemleak.c
> index 228a2fbe0657..73d46d16d575 100644
> --- a/mm/kmemleak.c
> +++ b/mm/kmemleak.c
> @@ -290,7 +290,7 @@ static void hex_dump_object(struct seq_file *seq,
> warn_or_seq_printf(seq, " hex dump (first %zu bytes):\n", len);
> kasan_disable_current();
> warn_or_seq_hex_dump(seq, DUMP_PREFIX_NONE, HEX_ROW_SIZE,
> - HEX_GROUP_SIZE, ptr, len, HEX_ASCII);
> + HEX_GROUP_SIZE, kasan_reset_tag((void *)ptr), len, HEX_ASCII);
> kasan_enable_current();
> }
>
> @@ -1171,7 +1171,7 @@ static bool update_checksum(struct kmemleak_object *object)
>
> kasan_disable_current();
> kcsan_disable_current();
> - object->checksum = crc32(0, (void *)object->pointer, object->size);
> + object->checksum = crc32(0, kasan_reset_tag((void *)object->pointer), object->size);
> kasan_enable_current();
> kcsan_enable_current();
>
> @@ -1246,7 +1246,7 @@ static void scan_block(void *_start, void *_end,
> break;
>
> kasan_disable_current();
> - pointer = *ptr;
> + pointer = *(unsigned long *)kasan_reset_tag((void *)ptr);
> kasan_enable_current();
>
> untagged_ptr = (unsigned long)kasan_reset_tag((void *)pointer);
> --
> 2.18.0
>
> --
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> To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/20210727040021.21371-2-Kuan-Ying.Lee%40mediatek.com.
next prev parent reply other threads:[~2021-07-27 7:11 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-27 4:00 [PATCH 0/2] kasan, mm: reset tag when access metadata Kuan-Ying Lee
2021-07-27 4:00 ` [PATCH 1/2] " Kuan-Ying Lee
2021-07-27 7:10 ` Marco Elver [this message]
2021-07-27 8:32 ` Kuan-Ying Lee
2021-07-27 9:34 ` Marco Elver
2021-07-27 19:22 ` Catalin Marinas
2021-07-28 11:05 ` Kuan-Ying Lee
2021-07-28 12:43 ` Marco Elver
2021-07-30 14:57 ` Andrey Konovalov
2021-07-30 15:24 ` Catalin Marinas
2021-08-04 5:31 ` kuan.ying lee
2021-07-27 4:00 ` [PATCH 2/2] kasan, mm: reset tag for hex dump address Kuan-Ying Lee
2021-07-27 7:20 ` Marco Elver
2021-07-27 8:54 ` Kuan-Ying Lee
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