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=1794063156; b=oUOlHMl6Y+v46JbEHUfVTUL/RAstM5n5uD/GTpT00LRoJ2LucY8JcFPCuqUCErgOvj9q fklJOJQg9FQFVPahhRAKBSnRVcz2d/lavU18Mdin9czdMIkiAfnuHNDFHQYtnE/uhsa33 UgpCvm452bXG4EB8l9y/4vmi2LFCGhHNJTXYJMqKLCx0N+5eDUOUq03xwMHQXjaqlAsOi JMSfEuwmv8u0l8c2/vtVq4YCCnyk58FjRJOTQFgjz5AZmWYNPN6/nBOw6DlGlZZ+wrJzY V62FE7vUBoY8Tdi3jok7DXB1VJSXkxHgqEeNOFQgpUM+OfrSB+QRUE0Y7HoQUnwmPIg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794063156; 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=itRltcLOtnouIHVcmdWR+2Wc9FfF2hNAP1aSaMllA5E=; b=Mm8/HzgcrutxDkH9Mi0SthnQluChEUBw7iFPY8n9xgqHb0BCpnsRefBTp8GCXC3VbTUk msutoFt40xXzSSwoZ+a4XrJAC+k8URTUgfujG/DFimGWlMd1vG1Io25Va1L4j0Q8G020P nQI9kymqVmxayvGsb7W2a+T1k/jV1CeIjwggRV0K+NZY1syXkikBXHTbkiEWmOOeYOh1S yYmbTSxRu+rsLHJWjflrperHawwBL6vZw5M1MNw5gEFYgQ8qQ6axEGMDP+NwL9EJqpPMY 7Zs5BeB2YJbHDz//RYZ5Cy3dqPc2h/VXpPRNm0NldXNQWk0WrOkCCZpGpNHveu5XgNw== 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=FGz53Enq; 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 21340606A331; Sat, 7 Nov 2026 14:52:36 +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=FGz53Enq Received: by smtp.kernel.org (Postfix) with ESMTPSA id CAEF51F0089F; Sat, 7 Nov 2026 14:52:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794063156; bh=itRltcLOtnouIHVcmdWR+2Wc9FfF2hNAP1aSaMllA5E=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=FGz53EnqznPq4GOBy4fTvEzs8eygg/vZpUuCnE+nmty26Kpi8/ygh14jakctBSkLE zOTvJaMcDu5mWO4qDBnm3pyarp3EybJEE49/4zPFX4ETZAJi1abbVw6gk+QH6uzjCf zdB3m94Wcf6HRAHGBIvfSLSyQa05mKH2riUXDxtI= 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 6.18 380/869] mm/page_table_check: skip zero pages Date: Sat, 7 Nov 2026 08:51:02 -0500 Message-ID: <20261107134906.021709789@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: 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: Signed-off-by: Sasha Levin --- mm/page_table_check.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/page_table_check.c b/mm/page_table_check.c index 91c4dacc41fb8..fa2c12e76a9e7 100644 --- a/mm/page_table_check.c +++ b/mm/page_table_check.c @@ -67,7 +67,7 @@ static void page_table_check_clear(unsigned long pfn, unsigned long pgcnt) struct page *page; bool anon; - if (!pfn_valid(pfn)) + if (!pfn_valid(pfn) || is_zero_pfn(pfn) || is_huge_zero_pfn(pfn)) return; page = pfn_to_page(pfn); @@ -102,7 +102,7 @@ static void page_table_check_set(unsigned long pfn, unsigned long pgcnt, struct page *page; bool anon; - if (!pfn_valid(pfn)) + if (!pfn_valid(pfn) || is_zero_pfn(pfn) || is_huge_zero_pfn(pfn)) return; page = pfn_to_page(pfn); -- 2.53.0