From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794474077; b=4tpePD9MJoknjRiR2Cbd6KDkyiW0FShW/6udrs5v5M5bmVIk9Iwu4ojT1uv68ib7MW5b +sltdeP9eXBm1wucpgSqJkH5dpvd5hhijzlJk7ZnrJKWZCBkYS+dLDV3FxYcryQG1K48d C3HcnLWkzxP112+qGEuKsDDD55Whiz29oDsfyNUdrnDJikr1zyT91lc5MAoPLx08287bE DXTJ87QGJ5yuRbfOnlY6KhuIPlTTANpASDXg01g1Q8Rn1q71A75WB5xNa4MV2QF7lyORs GhWE/6/UQtyPUK9mUKGPKsJ/VsbX8L8lYZ3WzCpRhdx6Tbtji9x0KYszniZWIlxhJbA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794474077; h=Received:DKIM-Signature:Message-ID:Date:MIME-Version:User-Agent: Subject:To:Cc:References:From:Content-Language:Autocrypt:In-Reply-To: Content-Type:Content-Transfer-Encoding; bh=Ui5EsWi10MV5QskRl/qxkNOLjqI3UUc/3+p5XFeUbrc=; b=DO/g6qtdjl9QNKh4Fgo1Ud4BmQtz8DHww6FhUlw4J0MSJ9KQXxvDBBMh7+L3Ip1o5V5S ul8G/dtVCkLiW7XTrOylhrXSsapKN0isbKhdCzi/1oGLAheSJB5ZuB3hkefU5bJp29DW4 IxvQRDWSUnP4sDd++R9DNMOV/CJm68VA8mXdq+xliK0alY5zKKWk7JT8/qtlt9OJOQIUh 4hm91wOqZw3pYIL6SYsW18Ewn33RcwUssJcyCWTHULCRMZlxNNjhD/p8S+f71JLQlN1ow G1HVUB4douJ5K9xWtffyHepTxH5TkuUG0dtzgxFY0GNXVIFSBe+W4n7BVJJ7WukHuvQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=P3e+l8T0; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 83568606A333; Thu, 12 Nov 2026 09:01:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=P3e+l8T0 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 38DBB1F00A0A; Thu, 12 Nov 2026 09:01:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794474077; bh=Ui5EsWi10MV5QskRl/qxkNOLjqI3UUc/3+p5XFeUbrc=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=P3e+l8T0gWTQb/C7XKzRiBY8pIKQ9krHWSQey3gWmvT07gJb4AFbqD9UhUewo471g XEY9QYW0g7nZRjYvUgpRE4T8D5lBHDPWr1XlwJrVi2olqY+EODn/0zsfm1wJ5y+67V HhPF++bqEkrHBuiFXLNcOEmM5jajda3NTpqLT3qgQZ7HM7TX95ZOuTaUslLXHs2eW8 NSP+NG8fPY5Uw0/qUVBSbvHEy+LEWOYR+aAKHQKGY+Y1JTdkXJcB+7FPjUs6i4zScq k6Rsb5kL5gMbQX1pnquucYeGPftg6vODKOs1CuK5fK2R2aLWz1PX1fZxwxlqMSat6y 6ck8qsAfMYUiw== Message-ID: <6f5d77fe-213f-44d1-b5e5-551de03eb903@kernel.org> Date: Thu, 12 Nov 2026 09:57:38 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/3] fs/proc/task_mmu: don't read young/dirty from a non-present PMD in smaps To: Usama Arif , Andrew Morton , apopple@nvidia.com, byungchul@sk.com, gourry@gourry.net, jannh@google.com, joshua.hahnjy@gmail.com, liam@infradead.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, ljs@kernel.org, matthew.brost@intel.com, mhocko@suse.com, pfalcato@suse.de, rppt@kernel.org, surenb@google.com, vbabka@kernel.org, ying.huang@linux.alibaba.com, ziy@nvidia.com, kas@kernel.org, hannes@cmpxchg.org, riel@surriel.com, shakeel.butt@linux.dev, kernel-team@meta.com, baolin.wang@linux.alibaba.com, Nico Pache , ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev Cc: stable@vger.kernel.org References: <20261111113904.650722-1-usama.arif@linux.dev> <20261111113904.650722-3-usama.arif@linux.dev> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/11/26 12:38, Usama Arif wrote: > smaps_pmd_entry() passes pmd_young(*pmd) and pmd_dirty(*pmd) to > smaps_account() for every PMD, including migration and device-private > entries, where those bits hold part of the swap offset rather than > accessed/dirty state. smaps_pte_entry() only reads them when the entry > is present. > > On x86_64 the offset is stored inverted across bits 9-58, which overlap > _PAGE_SAVED_DIRTY, so pmd_dirty() returns garbage: a clean 2MB > device-private mapping is accounted as 2048 kB dirty, and lazyfree > accounting is suppressed. pgtable_64.h also warns that the hardware can > set the accessed and dirty bits on non-present entries by mistake. > > Only read the bits when the PMD is present. > > Fixes: c94b6923fa0a ("/proc/PID/smaps: Add PMD migration entry parsing") > Cc: stable@vger.kernel.org > Signed-off-by: Usama Arif > --- Yes, thanks! Acked-by: David Hildenbrand (Arm) -- Cheers, David