From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 5CF0FD531; Tue, 14 May 2024 10:56:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715684199; cv=none; b=rEp+5TGefgMbCzmoMJm+ER4Ugh1kSOgt4yblOGdtXA/KNgfLDsQTidt8N/O/f9nHmLwBRvIv5PsOJzu9jf9IPJW5rjFb8Z3IA0oT0Cp7LTXCxv7rW6vh+YvsJBs8gvU8Xa1UNk5rdHNZvW+lTwoMbMTu3ROLwsSQbeq247akWgw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715684199; c=relaxed/simple; bh=bL9jNkWNmhpSTIHfYQm3hWiZJNf/DyVDr1GYDIJMyQc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=b0AYdzytBFATrtN9oCYdEM6xZZup24BB0bBTVHep81jsnopQBm5lQJERzQA+3DUdEPyAg6oyE7Vnx/yuZ1j71kosquYkNE+ARiBFpxZJl2bA2cGfnUSmg0Y0W8smsPH8Ugnpy8yVrfDAQQe/IIUp5ryMPVn/Jd09vzeQ8PuK9U0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=19ZiBuKu; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="19ZiBuKu" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B6677C2BD10; Tue, 14 May 2024 10:56:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1715684199; bh=bL9jNkWNmhpSTIHfYQm3hWiZJNf/DyVDr1GYDIJMyQc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=19ZiBuKutZgr2uEvn8ddAu7fBilOAHJgNJq+qUNnQtgEmoEA0x/KzjJFQIXGgAjzP iI0Ik/AbhlHB5caPjCvd3OwjCHceCCIQgGFwGyf4fhY3FK9Ep1UvpKmTIY1g86qepC vbjy2Ox7dpT/mdhn4ypDEW/WcnpgR+qUNgtbJ+7o= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Ryan Roberts , David Hildenbrand , Muhammad Usama Anjum , Peter Xu , Andrew Morton Subject: [PATCH 6.8 317/336] fs/proc/task_mmu: fix loss of young/dirty bits during pagemap scan Date: Tue, 14 May 2024 12:18:41 +0200 Message-ID: <20240514101050.588753452@linuxfoundation.org> X-Mailer: git-send-email 2.45.0 In-Reply-To: <20240514101038.595152603@linuxfoundation.org> References: <20240514101038.595152603@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.8-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ryan Roberts commit c70dce4982ce1718bf978a35f8e26160b82081f4 upstream. make_uffd_wp_pte() was previously doing: pte = ptep_get(ptep); ptep_modify_prot_start(ptep); pte = pte_mkuffd_wp(pte); ptep_modify_prot_commit(ptep, pte); But if another thread accessed or dirtied the pte between the first 2 calls, this could lead to loss of that information. Since ptep_modify_prot_start() gets and clears atomically, the following is the correct pattern and prevents any possible race. Any access after the first call would see an invalid pte and cause a fault: pte = ptep_modify_prot_start(ptep); pte = pte_mkuffd_wp(pte); ptep_modify_prot_commit(ptep, pte); Link: https://lkml.kernel.org/r/20240429114017.182570-1-ryan.roberts@arm.com Fixes: 52526ca7fdb9 ("fs/proc/task_mmu: implement IOCTL to get and optionally clear info about PTEs") Signed-off-by: Ryan Roberts Acked-by: David Hildenbrand Cc: Muhammad Usama Anjum Cc: Peter Xu Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- fs/proc/task_mmu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -1826,7 +1826,7 @@ static void make_uffd_wp_pte(struct vm_a pte_t old_pte; old_pte = ptep_modify_prot_start(vma, addr, pte); - ptent = pte_mkuffd_wp(ptent); + ptent = pte_mkuffd_wp(old_pte); ptep_modify_prot_commit(vma, addr, pte, old_pte, ptent); } else if (is_swap_pte(ptent)) { ptent = pte_swp_mkuffd_wp(ptent);