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=1794591467; b=WZ1IOFe1JZ79rOftcjZ44qFPCiIlRa7OoMKkFNMA0HbINNt9R0LsjPAdKx69BOrDNjnL 2rX3GzqFGRco5jwzR4RARewmpogy1hCFwxZS9vwjWOYdebpIW55to4UTrVYwR7WwHwm1l sI6geirLGnoDFiTYPqyVQf5wrEfH3flP4j8PZbko1HbcOROeEVTaTie+PH4htP5tj/EsM BX8MJZS5w2k9E84W3VJnW5CX+w+tkmut+3rXbTR7T4eqVyNxxsU5CfPZlfF4eaN18dEtA UkoPpisQKvyNBD/Va/9LgcfqJqpVV4sf95mnKBtYiD+0kU7wiOqcilzOtmFViD/8Nxw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794591467; 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=q6veOhloNQ6o6Nn+jhflBlJrSqv5CdK9icqe6Udnclg=; b=G4A0qEZ1UJaFWJEkQN5UBeCe7utCZMH30HedSdZtUq4JGu2S613hR0/q8J/r33ePjTPb wLTeyPLIdfcszhWpbsFzwShM9JWSRn28pPwj+PCVAPLiMdSBxKfu5Y39N1JZ/E0CCePZU uril+zPtEZ1+ezNiU6ziJu2rBQ30RRtv8SYFtlTgtb+KDtg1Pv538VKuE1h4+AWVraZPh Y66uENsnQoNsA1PXwzn1aOCOAgBMwYXpPOp7DCJTWPdi/nudl0zOo5yNsE04FvpS8mqgJ 2hKrW9AbRaK6eBxfhOs1NwhddrCuG/mZ9B3730gSJWlbsc4N5d4Zcy9Z/dp0XD6QVyA== 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="Wr/395RT"; 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 45048607D2C3; Fri, 13 Nov 2026 17:37:47 +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=Wr/395RT Received: by smtp.kernel.org (Postfix) with ESMTPSA id EC3BD1F000C4; Fri, 13 Nov 2026 17:37:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794591467; bh=q6veOhloNQ6o6Nn+jhflBlJrSqv5CdK9icqe6Udnclg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Wr/395RT+lc0zhzf1wzVIUglyC0KZPIxf1MbQSkjRx02TY71A3SKtBvXnP8HNGMBf fuYBQ1C8BE0b5dJxdvCRGeUHMKaiMIiKwjo/vT3DFVaBILnAirDIbwAT0YENDiiZxJ xwn3HxkrTPSg7t5FAtbWMiu4LG1+yXS4pVb+3dBM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Zhiling Zou , Ren Wei , Andrew Morton , Vega , Ye Liu , Sasha Levin Subject: [PATCH 6.12 551/670] mm/page_table_check: skip zero pages Date: Fri, 13 Nov 2026 10:51:55 -0500 Message-ID: <20261113153830.554594495@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261113153811.177190860@linuxfoundation.org> References: <20261113153811.177190860@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 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Zhiling Zou [ Upstream commit 33afd07412a1efe5b750a3fd5eb0272ebdd12761 ] page_table_check_set() accounts pages by whether they are PageAnon(). The shared zero page is a special page, not an ordinary file-backed page. Read faults on private anonymous mappings can install many read-only PTEs that point at the zero page, but page_table_check currently accounts them in file_map_count. That lets an unprivileged process populate enough zero-page mappings to overflow file_map_count and trip the BUG_ON() in page_table_check_set(). Skip zero pages in page_table_check accounting. They do not need the anonymous/file mapping conflict checks that page_table_check performs for ordinary pages, and this keeps the existing counter size and page_ext layout unchanged. Link: https://lore.kernel.org/1f8848512d2e3ded944f8d595c29faee8fdaeab0.1784645969.git.roxy520tt@gmail.com Fixes: df4e817b7108 ("mm: page table check") Signed-off-by: Zhiling Zou Signed-off-by: Ren Wei Signed-off-by: Andrew Morton Reported-by: Vega Assisted-by: Codex:gpt-5.4 Cc: Ye Liu Cc: [ sashal: Replaced unavailable is_huge_zero_pfn(pfn) with is_huge_zero_folio(pfn_folio(pfn)). ] Signed-off-by: Sasha Levin --- mm/page_table_check.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/mm/page_table_check.c b/mm/page_table_check.c index 2efa910eef23e..1076f8e055f31 100644 --- a/mm/page_table_check.c +++ b/mm/page_table_check.c @@ -67,7 +67,8 @@ static void page_table_check_clear(unsigned long pfn, unsigned long pgcnt) unsigned long i; bool anon; - if (!pfn_valid(pfn)) + if (!pfn_valid(pfn) || is_zero_pfn(pfn) || + is_huge_zero_folio(pfn_folio(pfn))) return; page = pfn_to_page(pfn); @@ -107,7 +108,8 @@ static void page_table_check_set(unsigned long pfn, unsigned long pgcnt, unsigned long i; bool anon; - if (!pfn_valid(pfn)) + if (!pfn_valid(pfn) || is_zero_pfn(pfn) || + is_huge_zero_folio(pfn_folio(pfn))) return; page = pfn_to_page(pfn); -- 2.53.0