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=1794063152; b=RlX4GOt79ZDC0uzyUo+ktbI1lLrmkISSGr4nTh95OkfcKc5AXisLv9s9k1wBXoLvTIck vtXZo2iMjjeAg6lMp31U5EBLCdgnwuAP+oGXUr9w8Ux0qHMEFnn6dtSMEzTeYgJvdaZ0n XjW1eS7829+f0die+T0Wtgmtn1GwEf+2fSFa8SNYLquLTJkoJpyqe69ECYgtbSJCeJH0F zWKH9LLNXLK4UWjhisXzlbEpg+Bv3F7Q8Eu5GaIRxBHMSMyScs9odCGroFb2qcvcz7R2e GZHuQahGtYWCFOp5vKONJqS+VKyVa92t4GiXnMAvVCBYIqAZNXqSuBrkdSFcHiGJixA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794063152; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=s2blUkX7tqH9bQNhda4hbOIMH6UhuZl8rDQklCKwSFQ=; b=Cp9MC0JrBF0Deg7SWNBk/5HZ3GaOifNmsCcjyF7hM94WLfX+qqwCpOL02plBsRZugAWd OaFip1sH34nfQBIrEVB1lWt4D4PoDdq6Z0s7D/Jpgip6L1pDaTBP+W1i2JR84dAGyfXsB 56Bv6KwmWfUIEuqupTx/mMG1EYM4lXhi83JHByzFnlQls7+XECbsWgryr/er7FCex/kuu v5fuZklUdXGmmYIR3nWiDcIeNtiKnh54enmipXoZIdD5Rn4CEHHLYGo/uveuwVXD16Iom +RiiAycD47+SRFk68veUIXgDC/lBWwQf1jjg4i8im2ZLBcKIgE3XbordqcsKQPju1RQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b="C/07EYKj"; 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 7DE11606A331; Sat, 7 Nov 2026 14:52:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=C/07EYKj Received: by smtp.kernel.org (Postfix) with ESMTPSA id 16CB11F0089F; Sat, 7 Nov 2026 14:52:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794063152; bh=s2blUkX7tqH9bQNhda4hbOIMH6UhuZl8rDQklCKwSFQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=C/07EYKji01dsK9lcDmETmS6rB0+XxMalTMiiwnccCzEph79jno7ceBbJm0gL5LTS f8aLIGaRPmeZW2k++oP3nIp/PTYAlmugmjD91/P5XZWWkFHls49q1jRhMhKeCOanyG 7JtGPP3nXM8paGzBwIhDkHHY1MqmmjbCgcbp4Msc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Qi Xi , Andrew Morton , Zi Yan , Brendan Jackman , Johannes Weiner , Kefeng Wang , Michal Hocko , Nanyong Sun , Suren Baghdasaryan , Vlastimil Babka , Sasha Levin Subject: [PATCH 6.18 377/869] mm/page_isolation: guard compound_order() against racing Date: Sat, 7 Nov 2026 08:50:59 -0500 Message-ID: <20261107134905.895506408@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261107134852.069646174@linuxfoundation.org> References: <20261107134852.069646174@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Qi Xi [ Upstream commit 4c767c5dd9bc3521fed11e6fe1d52621fe5abf7b ] The PageCompound branch reads compound_head() without holding a reference. A racing split or free can cause compound_head() to return a stale pointer, and compound_nr() reads the order from that stale head, leading to out-of-range shifts and making the skip distance meaningless. Read the order explicitly with compound_order() and validate it is within MAX_FOLIO_ORDER before shifting. Also verify the derived head_pfn against the legitimate pfn: the head must not be past pfn, must be aligned to nr_pages, and pfn must fall within the compound page. Bail out with -EBUSY if any check fails. Link: https://lore.kernel.org/20260825120549.966271-3-xiqi2@huawei.com Fixes: b2c9e2fbba32 ("mm: make alloc_contig_range work at pageblock granularity") Signed-off-by: Qi Xi Signed-off-by: Andrew Morton Suggested-by: Zi Yan Reviewed-by: Zi Yan Cc: Brendan Jackman Cc: Johannes Weiner Cc: Kefeng Wang Cc: Michal Hocko Cc: Nanyong Sun Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Signed-off-by: Sasha Levin --- mm/page_isolation.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) diff --git a/mm/page_isolation.c b/mm/page_isolation.c index 2ec974fa9726d..2e366e7bd5e93 100644 --- a/mm/page_isolation.c +++ b/mm/page_isolation.c @@ -411,10 +411,28 @@ static int isolate_single_pageblock(unsigned long boundary_pfn, if (PageCompound(page)) { struct page *head = compound_head(page); unsigned long head_pfn = page_to_pfn(head); - unsigned long nr_pages = compound_nr(head); + unsigned int order = compound_order(head); + unsigned long nr_pages; + + /* compound_order() is racy. Cap it at MAX_FOLIO_ORDER. */ + if (order > MAX_FOLIO_ORDER) + goto failed; + + nr_pages = 1UL << order; + + /* + * compound_head() is also racy, so the derived head_pfn + * needs additional checks to make sure it is valid. + * Otherwise, just fail the check. pfn comes from + * __first_valid_page() as a legitimate PFN, so use it to + * check head_pfn. + */ + if (head_pfn > pfn || !IS_ALIGNED(head_pfn, nr_pages) || + pfn - head_pfn >= nr_pages) + goto failed; if (head_pfn + nr_pages <= boundary_pfn || - PageHuge(page)) { + PageHuge(head)) { pfn = head_pfn + nr_pages; continue; } -- 2.53.0