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Fri, 06 Feb 2026 11:07:24 -0800 (PST) MIME-Version: 1.0 References: <202601071226.8DF7C63@keescook> In-Reply-To: From: =?UTF-8?Q?Maciej_=C5=BBenczykowski?= Date: Fri, 6 Feb 2026 11:07:12 -0800 X-Gm-Features: AZwV_QhSTkSJ_KynPb24QBIc0N9LtzMU3n-qIIiw27uPu35C6AHY-mN4QWU-75A Message-ID: Subject: Re: KASAN vs realloc To: Maciej Wieczor-Retman , Andrey Ryabinin Cc: Kees Cook , joonki.min@samsung-slsi.corp-partner.google.com, Andrew Morton , Alexander Potapenko , Andrey Konovalov , Dmitry Vyukov , Vincenzo Frascino , Marco Elver , Andrew Morton , Uladzislau Rezki , Danilo Krummrich , jiayuan.chen@linux.dev, syzbot+997752115a851cb0cf36@syzkaller.appspotmail.com, Maciej Wieczor-Retman , kasan-dev@googlegroups.com, Kernel hackers , linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: D832620010 X-Stat-Signature: swbmxkdgwwu5mnapwhgmwfxcs9zsdjfb X-Rspam-User: X-HE-Tag: 1770404845-66547 X-HE-Meta: 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 yfPvSafe kE/xaITqP0/yVlqZATUSZ6kn7Al+xXf6N/j2UybEtJSar7t7nvziLOoMXNeE6CYtL6Ho9o6zZF5zVBAV/YomkwmudT7muPB6oTcUtQ7z3/h58Gh62TvbLr9KakGLB2MXMn04EdqWT2mdCY2S0iWBIpCZsKT35c9UBaLdno+kMBlxiVzO0QQhGKJXBOPzMfQOUtFTJqbgc5NNzXsFzjpX4nfbrj4P6XTzEpGDWNq73smSqoEk2lq9+4lFlQ2C0X2QRt5yHPHQDuw56WrDUusFQ3ZAjh8rwv8PV8smUFe9CscqbgQvU039LHZw8a0qrsK7dIGxNS0+xBp95CgpOMB5ziBHZJjyiwH7sHRmhU91ZG5ilCva12mu/pyCRPAahDDC7xmrG X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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.