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bh=x9mSUklrAV+WI1SjDDeOL740XIVyg2KNk0EDeh71PmU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=ktoPCjIar8FYAQBbdT94SfsFIp3xI7s/Hl+QX+pc1n52yYONEeoI2Jq4lkKx3luT4 9PS1aOACTPW0IUjkI6z33CJfiO0N7XZr5iI1BkZin8Fl07RHhzF//9nXas48qsrRUU TywccEiI2ial3G0J3ypgUZi7Jcb82M9SeOasF3Gw= Date: Tue, 24 Jan 2023 12:45:04 -0800 From: Andrew Morton To: andrey.konovalov@linux.dev Cc: Andrey Konovalov , Marco Elver , Alexander Potapenko , Dmitry Vyukov , Andrey Ryabinin , kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrey Konovalov , Peter Collingbourne Subject: Re: [PATCH mm] kasan: reset page tags properly with sampling Message-Id: <20230124124504.2b21f0fde58af208a4f4e290@linux-foundation.org> In-Reply-To: <24ea20c1b19c2b4b56cf9f5b354915f8dbccfc77.1674592496.git.andreyknvl@google.com> References: <24ea20c1b19c2b4b56cf9f5b354915f8dbccfc77.1674592496.git.andreyknvl@google.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: e4whxr9op6gdn8nu6qkrwys3ta4fsg9t X-Rspamd-Queue-Id: 53E2E40013 X-HE-Tag: 1674593108-907222 X-HE-Meta: U2FsdGVkX19VxHIuqbfhijgFujcnztVzQbVngt55P0jlXb29fFbtsRlm72Jgq3bCrMfWu3no9KBhXZClgVOORhJPxomITi1vJDR9tJ7hTc130KozIIPzl4CLi4MAmqP87rKMMzaAW20uVo/CvryCQs3LWYLW96YXDfTlxsSnhttniKI+y5ARvlXas9PGVt4xh8C0/OPInmd7HYD2cDJ0+EuhJ4S4GwHiTEN6Ipt6RwxVqC4x1PTDU0O72G8FKUD7HIL8WkDRrKWfzV3QvLng4sqvw3RB7mIH0Dw6rgjzwwwEPnzwdC/trx4Ea4gcfAckFw0Ez0J3IQNNz6a+fvjCUQb/Ds27fTd2TceF33vbwAkpNcyhOrKPb0A4chr75FivlxjMx3KcMXzMtkmzk/B4teGae2pTXuiCy6S4GgIwydtkl/hnIBde3Z3m/Hfovhkq63RndikBtv6HJIuGgktkwvMQMLmKqvJiVRmH9yUxnZpH928a0d5tTImjBFYwfeddY25zH+BOJC3d6DFt0OjGCy9RvF5AeyfkoKnRwr8nxSIN0oV9iQSSwIqdxRDl2/9ycFkZvY+/av3XdHRa2cKawekSQsL60IlBBi9dVqpiK/usJBUCjst2oC1PIt4NW+IFirv2MI0YZQTznFS06kOwRGaIHkFahx5FopsfJY5tR5bi1h1cKhq1hmf8A3UVqOiMlObNM0w7Zji0ZmXbCgXidsegW+LEf9kD4FFbvSQrZ3IoBkck+lpgtae5wFYWZJcLj5RF0gkPKS1oa3eIZPoSdylq/Qb2G5WlTjv97hP8C6kaYlF8WNhFEbBe+sSCPze2tqWCSPuvvxhXc+LMEnkmSHEd0+kgcri+JQ6O0c7gU+QDcfgVVjEOHW7WAfKaLnrZV2ez9BkbsQKL+wz8pW0IXab4svFf6Bf/m5o4L0OCDVmbADrX6FS6xM4MSSQATxrQMiPbcpqgZbKHxMUWlgD W6Q3KhRF 3hQOY80GiJITHdj0SW8TpAAvSkw9Xyg6QcTQdvfLmcykoALk5E14hPTApp81tTzVNq7MhM843rDh3VbxMdZszdD65Xl86OR0x0CgCxM4FNL90vJ4O397CCbfyzbC5ERcU1w18qzNyyvBhEdO3FwK4Yuk+9SWLbeZU+CMKvvO6CzpzdBymyRoFb+Vgj00uwzsgUiSZYDLtjY4f6OWthhIcLn1roDE2Xa/hI4eS2b9gq5EK9Kz+b5w2NDchOBHKMl85fuEaegAWvc5ZQFrzyfWzMiSwRPnjRkI05IW2aUYG8LauDkwXuT7RzMiNoyotAo9737pIXWBUXXUpNePjj0klC0c9OrYwnLwNmOcyMY3j9mu/GE3h8bgOAvNgmdwJg9Z7J0EErCocZxMHPsPzo0Eyo7/nI6Zayymh2CoG 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: On Tue, 24 Jan 2023 21:35:26 +0100 andrey.konovalov@linux.dev wrote: > The implementation of page_alloc poisoning sampling assumed that > tag_clear_highpage resets page tags for __GFP_ZEROTAGS allocations. > However, this is no longer the case since commit 70c248aca9e7 > ("mm: kasan: Skip unpoisoning of user pages"). > > This leads to kernel crashes when MTE-enabled userspace mappings are > used with Hardware Tag-Based KASAN enabled. > > Reset page tags for __GFP_ZEROTAGS allocations in post_alloc_hook(). > > Also clarify and fix related comments. I assume this is a fix against 44383cef54c0 ("kasan: allow sampling page_alloc allocations for HW_TAGS") which is presently in mm-stable, yes?