From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0EA1B3F12D5 for ; Thu, 9 Jul 2026 08:24:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783585450; cv=none; b=dcd6UkVi5JSBbA/vBSeSVBT6TLwDSJwPFjFm7a8P+twRAr1cAvnqpnSblne/2KaBhrLkswoIMNtqN0GzooMyiQlom1AwmO896z8/GjTDsjKqLOBPLIaNWGx60OUdXRj9y+2Sd0c65NNmfwCjZBtLqqUFIS/rE8i2X25TpqNSWCE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783585450; c=relaxed/simple; bh=k97/UQR0ZOZG7oOHp0/eqGUAtXhQQ81X/zMjplgAz+c=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=p1oRuF9Pl5qsFGlrLsrYwY/PDhlyf4coxJgSNydDBhCuBhA61+pXpz0DB+9AeDP3TDKkkASlaTukT3XzFr3yibVCjMsAP0d7AnpVB2y3TtM1U2y/DsO8ZV7CEW9wjnCdIWK2crZ1+Sy+IQP+QulAiH9VG0Zenk1sPsKuTAQTeNM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Vj2jr+Ri; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Vj2jr+Ri" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D61FF1F000E9; Thu, 9 Jul 2026 08:24:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783585449; bh=dfjX/HpXJM9iYsHnQmF5Xud/G0l8dqRVgfzx5MY/UdU=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Vj2jr+RizoHzfnZ5p2FylBywsVmOpAC2plcgd7ldnfHG6OAUX6knGZHbaw+PMAt8e LYSWzFiZVgZktom1pFDjjT4vwZa9Da5lTS+60/iOtp4K2T47YtDDADC0DbDKIIDdH/ 3pSCAAoKssrVJlFRxWcODnqg1alpP2Faxk8Isx+hmaXP8Z7JraeT7j9tfwUbo+simF DIetRp+Vh0TsWVqh3YXzVQoZswWV25iCKe/slSrGDf96LujHx2F5OdVieWuKb2DoEh fOpQ0izNXig6tRA/HCi6B+wYfS9yielZg91S/BrouO2Ht21xkbphxg2cm52U8Lau0v qIh8Lzku+3+Sg== Message-ID: <9fc67666-ac70-4d03-8836-5f8a9f5f1ff6@kernel.org> Date: Thu, 9 Jul 2026 10:24:03 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 4/5] mm/page_alloc: make sure tail_page->private is zero at page free time Content-Language: en-US To: Zi Yan , Andrew Morton , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , David Hildenbrand , Lorenzo Stoakes , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Mike Rapoport , Dennis Zhou , Tejun Heo , Christoph Lameter , Alistair Popple Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260703-keep-subpage-private-zero-at-free-v2-0-2970fe777dd6@nvidia.com> <20260703-keep-subpage-private-zero-at-free-v2-4-2970fe777dd6@nvidia.com> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSNWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBrZXJuZWwub3JnPsLBsAQTAQoAWhYhBKlA1DSZLC6OmRA9UCJPp+fM gqZkBQJqFFy6GxSAAAAAAAQADm1hbnUyLDIuNSsxLjEyLDIsMgIbAwUJGtCBUAULCQgHAwUV CgkICwUWAgMBAAIeBQIXgAAKCRAiT6fnzIKmZJIUEADFx/tREzUImHrEwVHeSvDFmA7tJysI UVrlvrM09E7GIuzphzv7jYmo8n3ANpCczLEVr4G0syYQdTigaZgv3+FQDIIzhKih1IHhu1Ei XHlywNWKnQxxQEUNi5Mwx43wQz5XVw9F1A7gtKBKNtfogO511hAbrzagrYajyQacEJ/+sfhZ 9Da8ltHIXD8pcYaHUfQgEusCgmEd9+KrUwrTbckFKmYq5chuE6yJ4J0EmWknL096jIE6CnzF FRslQ3B1UKDjxVsm1ZHfir5NeWszLkTvGFsddFaWTgh8UycESG6VQzKXjjewXu2pG7YQYRpj QKm1W5X2TkwWkXRBZTmfmbhxIUMh3+zf5wQ463rSmDN/8v81tdqBtAW6rH/kzg1GvkaTHXn0 507yEHFzBksk2viAuIxxr7km8+/KARYLIdGtx30EG8cKzAUZOK6WqxtNCsXUJNrVE8CWrCaD icoNu7Fs1c5hmPHdSTnU48ce67449DdnO4neLSNhRiGlMHJgfJUmgrxu/hcYeOZ3haWmEQ2w uW1Mh01OHi8QZHCEyAbABrPs9GUgccc/4eYXX9hIgxfSkYzn8f+8NuIFPWl/0uTvjgqU29FQ SbzOLxHq9439Ox40G5mS5eZXRGxITYR+6TXvRGI6P/264jvflnr/pDGUttaikU+0W+1uxgKH cmYbEc7ATQRbGTU1AQgAn0H6UrFiWcovkh6EXVcl+SeqyO6JHOPm+e9Wu0Vw+VIUvXZVUVVQ La1PQDUi6j00ChlcR66g9/V0sPIcSutacPKfdKYOBvzd4rlhL8rfrdEsQw5ApZxrA8kYZVMh FmBRKAa6wos25moTlMKpCWzTH84+WO5+ziCTsTUZASAToz3RdunTD+vQcHj0GqNTPAHK63sf bAB2I0BslZkXkY1RLb/YhuA6E7JyEd2pilZOrIuBGl/5q2qSakgnAVFWFBR/DO27JuAksYnq +aH8vI0xGvwn75KqSk4UzAkDzWSmO4ZHuahKtQgZNsMYV+PGayRBX9b9zbldzopoLBdqHc4n jQARAQABwsF8BBgBCgAmAhsMFiEEqUDUNJksLo6ZED1QIk+n58yCpmQFAmfIHFQFCRYU6J8A CgkQIk+n58yCpmS2PA//bqN1LfcotmArgElsa+0EGZSQlYgK48pm8WAeTXTngudP9IJ4SuKY HR5RNjHcBeqN+Me0zxRqYzRb8nGanHEkDyf4Im8DQM8d6vbyU+FcPmG4skud4kgS1zMHnlVd SXfSIwKC/hKgdHG8aBV7545Lz9X6Iohea+94wneD0aw/hqF+QWewGZhWJriWAZtvEkzNjQOi 4U9F/trLten/x7bpphDSnDMKJtITbtzATT1Dq7o7VpIUK1nCTQALMuMjKCdi8OdU/+V+R3O4 0PXWvX8qrvqYapVbZ+9KqT74FsuB0Ya9uXwgBF2Q6cRuETZk5vqaqKxzqoQZCO8AOz/58j6O 2RHNy/mZEN+7tJ5Tsq42zVJ4jxsT8b9YplavCMsnBgDeRWhcbYhCyttoL7nYISyWg4kQYZ/P wIV3OuNv2f8iKYsxNsRuClOAF82+gvqOy1/1pprFjy8uo2pkoOrb63aOP3vO5VHnRKgra6dq NcaZ+c6J4H+nEJGi2SkHAUJz5oBzuThvPudLvPA/SK8sKoM01IRxSihev/S/5WLazXB1PGem OCbvzC1IjWJJraxiDJ5IygokapUa2RP7+WBR22skQ3SSl6G107QgWKSyTOGWEaRmV53vxQLV jXuCmzSSasTL60zq5yGrT4/DYQVSNEUiUbG4pYekxJujNeEDkUlky0Y= In-Reply-To: <20260703-keep-subpage-private-zero-at-free-v2-4-2970fe777dd6@nvidia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/3/26 15:47, Zi Yan wrote: > Any code using tail_page->private of a folio, a compound page or a > high-order page is supposed to reset it after use, otherwise ->private data > can leak to new page user and cause unexpected issues. Add a bad_page() > check at page free path for it. > > Signed-off-by: Zi Yan Reviewed-by: Vlastimil Babka (SUSE) Nit: > --- > mm/page_alloc.c | 13 ++++++++++--- > 1 file changed, 10 insertions(+), 3 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 762d9b6bc792f..723a52dfc80f6 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1376,15 +1376,22 @@ static __always_inline bool __free_pages_prepare(struct page *page, > #endif > } > for (i = 1; i < (1 << order); i++) { > + struct page *tail_page = page + i; > + > if (compound) > - bad += free_tail_page_prepare(page, page + i); > + bad += free_tail_page_prepare(page, tail_page); > if (is_check_pages_enabled()) { > - if (free_page_is_bad(page + i)) { > + if (free_page_is_bad(tail_page)) { > bad++; > continue; > } > } > - (page + i)->flags.f &= ~PAGE_FLAGS_CHECK_AT_PREP; > + tail_page->flags.f &= ~PAGE_FLAGS_CHECK_AT_PREP; > + if (is_check_pages_enabled() && tail_page->private) { > + bad_page(tail_page, "nonzero private"); > + bad++; > + continue; It could be moved to the already existing is_check_pages_enabled() block above. The flags reset doesn't need to happen before the check, no? > + } > } > } > if (folio_test_anon(folio)) { >