From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sipsolutions.net (s3.sipsolutions.net [168.119.38.16]) (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 8AF2537E2FE for ; Tue, 21 Jul 2026 11:20:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=168.119.38.16 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784632840; cv=none; b=VQEr5xSGjhpfoPPlkiD3G1q9EDCeNG8U6TBRFlwWPpzS4HFJmPE6v8S9X+5wIn7HPESLIJQzZV1Z+ShzX8NwfFMdgIXvGkqxwZ8vAVS2yxb0GZNOOs5KWLIDUzZvGgHM8tZpB1liTBl4SCX7Ugw3dZcc0k10ySvvplx4ITxVRzU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784632840; c=relaxed/simple; bh=oHHW7nX2/0Co9VfEwkSXj25ZJ+oDvMRUElhCYL6+uTc=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=ui6b3r0D2gRF3GvfjnoGUO3hZrM7LX8MBkOl4yTekfRQDaWjqH3Oa21nE335r6rjiUZ3DCYeS75QehlBLBM8YP8z+0K69/gBY8RhuipnQcipWt2KaKxYTiPMGZppQoZI6gDKGojhOsS+D1SOB1OJkDADtg+GLKXBsRz2wtrjrF4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=permerror header.from=sipsolutions.net; spf=none smtp.mailfrom=sipsolutions.net; dkim=pass (2048-bit key) header.d=sipsolutions.net header.i=@sipsolutions.net header.b=AuGT5hLl; arc=none smtp.client-ip=168.119.38.16 Authentication-Results: smtp.subspace.kernel.org; dmarc=permerror header.from=sipsolutions.net Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=sipsolutions.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=sipsolutions.net header.i=@sipsolutions.net header.b="AuGT5hLl" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sipsolutions.net; s=mail; h=MIME-Version:Content-Transfer-Encoding: Content-Type:References:In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Sender :Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From:Resent-To: Resent-Cc:Resent-Message-ID; bh=oHHW7nX2/0Co9VfEwkSXj25ZJ+oDvMRUElhCYL6+uTc=; t=1784632837; x=1785842437; b=AuGT5hLlz1Gs72KGMgEi0hOUsbr/eAWFSk7aILqaG8aueFM EVynGmQwJ1e8Yfgz73d3k5sDJi1HXJcQs/TB0HjA42wlvRTD565exrtvACM3acAWx0ItzuwzoIfnZ LvRab31d72J4GQ3yIR/XNxicr0J8Dk4XIU/OvcGDaf75D/roxgmZ1RdWHGeu+HpS8tZKbdXQjIXIP frYKFO5SnJsC+o7Yklv5CB8dDTaW/71rXLWFTt6PUZrSmWIiZ/qVwYMF54ve0w+guLGmfH7TLG1no nX9RPZfYUbCndzld1NzvtuXKYWOiwxv3o2PAiqv/e1qdUk6qOeOa0RYwtdN+t38w==; Received: by sipsolutions.net with esmtpsa (TLS1.3:ECDHE_X25519__ECDSA_SECP256R1_SHA256__AES_256_GCM:256) (Exim 4.98.2) (envelope-from ) id 1wm8WU-000000020Bh-2CQq; Tue, 21 Jul 2026 13:20:30 +0200 Message-ID: Subject: Re: [RFC PATCH 0/6] um: introduce pidfd_mmap()/pidfd_munmap() syscalls From: Johannes Berg To: Cong Wang , Richard Weinberger , Anton Ivanov Cc: Benjamin Berg , linux-um@lists.infradead.org, linux-kernel@vger.kernel.org Date: Tue, 21 Jul 2026 13:20:29 +0200 In-Reply-To: <20260710205324.1343217-1-xiyou.wangcong@gmail.com> (sfid-20260710_225357_064327_367AF1B5) References: <20260710205324.1343217-1-xiyou.wangcong@gmail.com> (sfid-20260710_225357_064327_367AF1B5) Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.58.3 (3.58.3-1.fc43) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-malware-bazaar: not-scanned On Fri, 2026-07-10 at 13:53 -0700, Cong Wang wrote: > This RFC adds two syscalls, pidfd_mmap() and pidfd_munmap(), that let a > supervisor install or remove a mapping in another process's address space > without target-side cooperation, and converts User Mode Linux to use them= . Seems simple enough, but I can't really comment on it. > As this is an RFC, the UML side _intentionally_ does not handle host > portability: it assumes a host kernel that provides pidfd_mmap() and > deliberately omits any detection or fallback for older hosts (which would > otherwise pick the ptrace path, or fail the seccomp probe). That belongs > in a non-RFC version and is left out here to keep the series focused on > demonstrating the impact on UML. Makes sense for the RFC, but I think the fallback to seccomp as-is might be useful still, we did see some benefit of seccomp and cannot necessarily update the host kernels _that_ quickly. Maybe do that only if forced by the user with seccomp=3Dinsecure or something, not pick it with =3Dauto and fail with seccomp=3Don if it's not available? That'd be good enough for us, and not really leave a potential security trap (that we have now for people who don't read the docs ;) ). johannes