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 B845C3B2FF1 for ; Mon, 29 Jun 2026 14:53:51 +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=1782744833; cv=none; b=Pu9J346OE1HURPsIooShS5N1CwExciCi7YYCh8X1+T09zy31fXUpsbhcIWyqKAtNW7l6Wr8ITXlikvEY97bOJPPiDDkL6H0WZLpfQmQF+h48oj5NhDWSyPwra29Gjjj9njzZWekTjxFhWKGe91tsMezStqinIFER6b5u6kD7B6k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782744833; c=relaxed/simple; bh=uNwW9nNXUofLPKoNchx2FRU9RZ5KdkiJUsk03dEKBDo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=s+KBd1JIXFPgRq2q03JbBCY5ub6y5FHl8T90l9+Yo0xReK2odrnlbn3l0KrkpS/ZtrCJLbtB+siF3IdIKB2ZCnB3Q6VRJX5yzhc6Bugna5URxJyEDz87GZz5GuIkDBxomVteq6Dvx/5BQEAECoVq08L11ilq+KULxX23VqxVO4g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=LlI2kWZj; 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="LlI2kWZj" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D2AC91F000E9; Mon, 29 Jun 2026 14:53:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782744831; bh=s4VhTl4gCqM8Ky+x9qzAr1fbtUEk7+DIkvjnRs42Zt4=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=LlI2kWZjYNMvV8j50tEwPH3CWa5JeNC84gTm0y/3FyhWfX32+yoreGPoFmnXkg2FF 25rsY0R3V7hxbqPdMg04oiRO7MSdlzM7YdnCmlicv7M7HllEiFD+FMMwmtQRLn4NMm nHW4e5Ovut2VHqkLRuQIqDMkYLCYz0sxCQ2IQAILrW8pIAEJTSxvAteAve4li3z11j 5xHtAxkK2xA2PK93Id3u5Je3BwN0BQ/ive/cCs2PkKQymRFw3uxN/aTIhGII8HFUDE n+IxgvV729xiQcbDTy39hFSJ8yrLer6wu28HjfK9M0ngHsRhD3NGYVTAaMl7R1P7iD g43yaRuo4Szmw== Message-ID: <43b67098-b9b3-448f-aa7a-43b7ef678e1c@kernel.org> Date: Mon, 29 Jun 2026 16:53:46 +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 3/4] mm/page_alloc: make sure subpage->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 Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260628-keep-subpage-private-zero-at-free-v1-0-f4ce3930d10f@nvidia.com> <20260628-keep-subpage-private-zero-at-free-v1-3-f4ce3930d10f@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: <20260628-keep-subpage-private-zero-at-free-v1-3-f4ce3930d10f@nvidia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/29/26 04:56, Zi Yan wrote: > Any code using subpage->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. > > Assisted-by: Codex:gpt-5 # add the missing "return false" after bad_page() > Signed-off-by: Zi Yan I noticed the word 'subpage' is now frowned upon ;) See https://lore.kernel.org/all/20260623125723.2503832-1-dev.jain@arm.com/ since this is about tail pages, just call them as such? > --- > mm/page_alloc.c | 12 +++++++++--- > 1 file changed, 9 insertions(+), 3 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index ee902a468c2f..13c2655e24fb 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1374,15 +1374,21 @@ static __always_inline bool __free_pages_prepare(struct page *page, > #endif > } > for (i = 1; i < (1 << order); i++) { i starts at 1 > + struct page *subpage = page + i; so "tail_page" is accurate? > + > if (compound) > - bad += free_tail_page_prepare(page, page + i); > + bad += free_tail_page_prepare(page, subpage); > if (is_check_pages_enabled()) { > - if (free_page_is_bad(page + i)) { > + if (free_page_is_bad(subpage)) { > bad++; > continue; > } > } > - (page + i)->flags.f &= ~PAGE_FLAGS_CHECK_AT_PREP; > + subpage->flags.f &= ~PAGE_FLAGS_CHECK_AT_PREP; > + if (subpage->private) { > + bad_page(subpage, "nonzero private"); > + return false; > + } Also why not put this check into the is_check_pages_enabled() block and handle it the same way? > } > } > if (folio_test_anon(folio)) { >