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Sun, 22 Mar 2026 04:29:55 -0700 (PDT) X-Received: by 2002:a05:6a20:244f:b0:398:78cb:d85 with SMTP id adf61e73a8af0-39bce9ddf3emr8634347637.13.1774178995435; Sun, 22 Mar 2026 04:29:55 -0700 (PDT) Received: from localhost ([240d:1a:c0d:9f00:be24:11ff:fe35:71b3]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-82b03bbebb2sm7205704b3a.14.2026.03.22.04.29.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 22 Mar 2026 04:29:55 -0700 (PDT) From: Shigeru Yoshida To: Andrew Morton Cc: Minchan Kim , Sergey Senozhatsky , Mark-PK Tsai , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/zsmalloc: copy KMSAN metadata in zs_page_migrate() In-Reply-To: <20260321104845.452d0f903a52d45d3b76894e@linux-foundation.org> (Andrew Morton's message of "Sat, 21 Mar 2026 10:48:45 -0700") References: <20260321132912.93434-1-syoshida@redhat.com> <20260321104845.452d0f903a52d45d3b76894e@linux-foundation.org> User-Agent: mu4e 1.12.12; emacs 30.2 Date: Sun, 22 Mar 2026 20:29:54 +0900 Message-ID: <87h5q8qez1.fsf@redhat.com> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 7YS9NaHvT9jzveqN59faA59hMSrfLld_-pralrROsWc_1774178996 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 1F02980003 X-Stat-Signature: txbibykcoiydwnhwmif1xg4w4gm4iwpn X-Rspam-User: X-HE-Tag: 1774178998-265626 X-HE-Meta: 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 AXjssD2O BlXTnzS9MpOqKUN/z2Oi8Ou420iKan+FuE8jUwdgRRuSREzih6bPpCPJ5wVEe9UteHJvFXf0P1Aj44sp3N6K3nrpzUyekvMzhCiHtNdzU7MetpHFJ+D37h4hIylisxNcNf2/gxCIJtF7L0YV2zUk2ZEdt5moCSGceiiY7pFkIAUmCI1KT9zuzzXcS+LPrlz8A79SaF8SAW093fI41tBKp2l3j3jUgAtbpPG8ySV+gdQXHFBHXFeQBHUWDNwRYk/1hMQn3IbaKBhUj4CuH/uKCHRmpfPuO4VzsSZSAcSyX47v7UB/+qZMkuF+6ymubbHBXd4oXTqrHmyaOFtECIakxnTd6AsHQverdnrLJDNrNYOa/pu0e5bLzrG4g/ysklt3a0o9UIWgmVgZ0bWYsu+giFGE3n74sdyFHmyRSlO9zl+W+TbbtHye1MtttFQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Andrew Morton writes: > On Sat, 21 Mar 2026 22:29:11 +0900 Shigeru Yoshida wrote: > >> zs_page_migrate() uses copy_page() to copy the contents of a zspage >> page during migration. However, copy_page() is not instrumented by >> KMSAN, so the shadow and origin metadata of the destination page are >> not updated. >> >> As a result, subsequent accesses to the migrated page are reported >> as use-after-free by KMSAN, despite the data being correctly copied. >> >> Add a kmsan_copy_page_meta() call after copy_page() to propagate the >> KMSAN metadata to the new page, matching what copy_highpage() does >> internally. >> >> Fixes: afb2d666d025 ("zsmalloc: use copy_page for full page copy") > > That's three years old. Can anyone suggest why this has only now been > discovered? I think it's because KMSAN is clang and x86-64-only, so very few people run it. Also, this only triggers when compaction actually migrates a zspage page, which needs significant memory pressure. Shigeru