From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta0.migadu.com (out-194.mta0.migadu.com [91.218.175.194]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0D8254AEBCE for ; Tue, 13 Oct 2026 15:40:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.194 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791906007; cv=none; b=YJb32NEqITQJ3O8WTws1zkczT2064ARJeQvuPA7NyVyvh9uFRN7YamuY9/fJghugZthMLHEHw+AJt2TIWPHhJsjctYWqWC51FcitVlKu1N4AaORv4f/zdKj8HvjGinsKK6XOLHs07AwOijcitKQpfBVmp1P+qNuvkxOO5LzzIi4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791906007; c=relaxed/simple; bh=wvI3yQEb1pra9snQf3HMPf0AqFlWoLGzhzZcKtUO3i8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=VHZp4mZzblUE/Ldv+gQwc0ebyJtDSOYUD3lVEqrqCUX5kjF6U/NaMFB3U8qOXGO+DTtFSdQIExgfKlTYNV/ORkVYqgRradQAg07T1hxxmBv2EA0oalcF/ucHoOy1DYXKzoMM/vc20y64uqrkzAjspb6U3EaZS8e7cEh3CBA+TV0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=CbIVFpFz; arc=none smtp.client-ip=91.218.175.194 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="CbIVFpFz" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=wvI3yQEb1pra9snQf3HMPf0AqFlWoLGzhzZcKtUO3i8=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1791906002; v=1; x=1792510802; b=CbIVFpFzbvBZ6HFblwi9Sb2Ng2vo/5CtHr8jdpUpJfyFP0rmHhgvjF6nrCEl3FMJIiJRgIr9 ZbTVdh9AQTmDCe9FB8/Vz8xt/XXiOxJkF47VA0MZ6d/yz2HAiJ2wybh9QD08SWvhHFaU5MWfNII rFg/yXiVkz6lsZ4pqqBAewts= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 0335801ba07d6e44; Tue, 13 Oct 2026 15:40:02 +0000 X-Mizu-Trace-ID: 0335801ba07d6e44 X-Migadu-Flow: FLOW_OUT From: Lance Yang To: zhaogongyi@bytedance.com Cc: catalin.marinas@arm.com, will@kernel.org, ryan.roberts@arm.com, dev.jain@arm.com, baolin.wang@linux.alibaba.com, lance.yang@linux.dev, mark.rutland@arm.com, akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] arm64/mm: restrict transparent contpte mappings to valid PTEs Date: Tue, 13 Oct 2026 23:39:53 +0800 Message-ID: <20261013153953.77575-1-lance.yang@linux.dev> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20261013093600.54995-1-zhaogongyi@bytedance.com> References: <20261013093600.54995-1-zhaogongyi@bytedance.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On Tue, Oct 13, 2026 at 05:36:00PM +0800, Zhao Gongyi wrote: [...] > >Fixes: 4602e5757bcc ("arm64/mm: wire up PTE_CONT for user mappings") >Cc: stable@vger.kernel.org >Signed-off-by: Zhao Gongyi >--- Good catch! Thanks! [...] >diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c >index 0acab179f..851fa2e44 100644 >--- a/arch/arm64/mm/contpte.c >+++ b/arch/arm64/mm/contpte.c >@@ -463,6 +463,13 @@ void contpte_set_ptes(struct mm_struct *mm, unsigned long addr, > if (!mm_is_user(mm)) > return __set_ptes(mm, addr, ptep, pte, nr); > >+ /* >+ * Keep the producer-side invariant documented in pgtable.h true even >+ * if a direct caller passes an invalid descriptor with PTE_CONT set. >+ */ >+ if (!pte_valid(pte)) >+ return __set_ptes(mm, addr, ptep, pte_mknoncont(pte), nr); set_ptes() is the only in-tree caller, and it already clears PTE_CONT before we get here ... no? Why not fold !pte_valid(pte) into the !mm_is_user(mm) check below and return __set_ptes() directly? if (!mm_is_user(mm) || !pte_valid(pte)) return __set_ptes(mm, addr, ptep, pte, nr); If a direct caller does pass a !pte_valid PTE with PTE_CONT set, I'd rather add a VM_WARN_ON() to catch that. Silently clearing the bit would hide a caller bug :) Cheers, Lance >+ > end = addr + (nr << PAGE_SHIFT); > pfn = pte_pfn(pte); > prot = pte_pgprot(pte); >-- >2.39.5 (Apple Git-154) >