From: Maciej Wieczor-Retman <m.wieczorretman@pm.me>
To: "Maciej Żenczykowski" <maze@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>,
Kees Cook <kees@kernel.org>,
joonki.min@samsung-slsi.corp-partner.google.com,
Andrew Morton <akpm@google.com>,
Alexander Potapenko <glider@google.com>,
Andrey Konovalov <andreyknvl@gmail.com>,
Dmitry Vyukov <dvyukov@google.com>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
Marco Elver <elver@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Uladzislau Rezki <urezki@gmail.com>,
Danilo Krummrich <dakr@kernel.org>,
jiayuan.chen@linux.dev,
syzbot+997752115a851cb0cf36@syzkaller.appspotmail.com,
Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com>,
kasan-dev@googlegroups.com,
Kernel hackers <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org
Subject: Re: KASAN vs realloc
Date: Fri, 06 Feb 2026 20:14:25 +0000 [thread overview]
Message-ID: <aYZJ2Ohug6b9Vth0@wieczorr-mobl1.localdomain> (raw)
In-Reply-To: <CANP3RGeHnhufYyc0P2OiKJbXdZjPW41TP=JS6nYk9xGRU8UuKQ@mail.gmail.com>
From what I see kasan_poison_last_granule() is called through:
__kasan_vrealloc()
--> __kasan_unpoison_vmalloc()
----> kasan_unpoison()
------> kasan_poison_last_granule()
and the arguments are "addr + old_size" and "new_size - old_size" so it looks
okay I think.
On 2026-02-06 at 11:07:12 -0800, Maciej Żenczykowski wrote:
>While looking at:
> https://android-review.git.corp.google.com/c/kernel/common/+/3939998
> UPSTREAM: mm/kasan: fix KASAN poisoning in vrealloc()
>
>I noticed a lack of symmetry - I'm not sure if it's a problem or not...
>but I'd have expected kasan_poison_last_granule() to be called
>regardless of whether the size shrunk or increased.
>
>It is of course possible this is handled automatically by
>__kasan_unpoison_vmalloc() - I haven't traced that deep,
>in general these functions seem to have a terrible api surface full of
>razors... with hidden assumptions about what is and is not granule
>aligned.
--
Kind regards
Maciej Wieczór-Retman
next prev parent reply other threads:[~2026-02-06 20:14 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-06 12:42 Maciej Żenczykowski
2026-01-07 20:28 ` Kees Cook
2026-01-07 20:47 ` Maciej Wieczor-Retman
2026-01-07 21:47 ` Maciej Żenczykowski
2026-01-07 21:50 ` Maciej Żenczykowski
2026-01-07 21:55 ` Maciej Żenczykowski
2026-01-09 18:55 ` Maciej Wieczor-Retman
2026-01-09 20:05 ` Maciej Żenczykowski
2026-02-06 19:07 ` Maciej Żenczykowski
2026-02-06 20:14 ` Maciej Wieczor-Retman [this message]
2026-02-06 21:26 ` Maciej Żenczykowski
2026-01-13 19:15 ` [PATCH 1/2] mm/kasan: Fix KASAN poisoning in vrealloc() Andrey Ryabinin
2026-01-13 19:15 ` [PATCH 2/2] mm/kasan/kunit: extend vmalloc OOB tests to cover vrealloc() Andrey Ryabinin
2026-01-15 3:56 ` Andrey Konovalov
2026-01-16 13:28 ` [PATCH] mm-kasan-kunit-extend-vmalloc-oob-tests-to-cover-vrealloc-fix Andrey Ryabinin
2026-01-16 18:53 ` Maciej Wieczor-Retman
2026-01-17 1:16 ` Andrey Konovalov
2026-01-14 12:17 ` [PATCH 1/2] mm/kasan: Fix KASAN poisoning in vrealloc() Maciej Wieczor-Retman
2026-01-15 3:56 ` Andrey Konovalov
2026-01-16 13:26 ` Andrey Ryabinin
2026-01-17 1:16 ` Andrey Konovalov
2026-01-17 17:08 ` Andrey Konovalov
2026-01-19 0:48 ` Andrew Morton
2026-01-19 14:43 ` Andrey Ryabinin
2026-01-19 14:45 ` [PATCH] mm-kasan-fix-kasan-poisoning-in-vrealloc-fix Andrey Ryabinin
2026-01-20 17:46 ` Andrey Konovalov
2026-01-21 16:01 ` Andrey Ryabinin
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