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 B70043B1B3; Thu, 16 Apr 2026 13:28:11 +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=1776346091; cv=none; b=juYRU6XRtTn5pWTGJtUDTr9WRmSMa7grtkSXPsMMHNHAkbJTNqlBK3ZvhIBmb5AeYvJsjf2r9bW+J6ZRFksHF49rIu9aN6Vrao4o6fB9+TP2eQkLt2EjdATk4hycztS2sBQ3VNKMt04dIYzz+FhE+0YYfPVPR1pIcLFkgKtGcWY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776346091; c=relaxed/simple; bh=J12G5pzMTUvfefHA+A/ErGNi+UxZvMBPAb5e+FOj0Hk=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=dcB9tgmPn0FXwaWojcTe7av/GiuKSx6AmhF4aP0oHamMyK+2TSwTOzhrkBf7o2F74WvMHgqsRihJMyUiOvNyX6Pf1qlI9DsF2UYd/KAjEIpQ8to1tK6zvszr8J9Wk0HDqSCLkj9pcrhA9BOY/ADr+MtmpdQCDkxmfEDuYS123x8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=VNITp2US; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="VNITp2US" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F28C0C2BCAF; Thu, 16 Apr 2026 13:28:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776346091; bh=J12G5pzMTUvfefHA+A/ErGNi+UxZvMBPAb5e+FOj0Hk=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=VNITp2USm8xN92IVKtT3+Bm1/bo7k1/3Ai5Mbub5YTyQI4sLUyzogUBZUDB+Sg1Qr xOUGj6hRn+20kW6zfJViUk8cEXLUn6+v83HVLAOS64KeTf0p8UvXz1AadMfurbISg7 ITwO5OCaw3lGxtGrLNH3oZiDNZyVHqC7KvnhkTn9d6GjmqaE5yUqMORfohU1MAs55p Sx+pC8m+/F85O6fxsTnVjvE2Loqs98Sak0hqle1cs81EtPWpjLCN/RQrx14DLlC3zM 1YHudu8Ktsej3arbGg5n0I5zMTfo4uglwL7knPO1BM5xiGyt7odnDxP7rAEBhXwl8A Q7GAfPoJ+12QA== Message-ID: <9ce53137035dfca329aa5e49593154149be3ac49.camel@kernel.org> Subject: Re: [PATCH v6 1/4] openat2: new OPENAT2_REGULAR flag support From: Jeff Layton To: Aleksa Sarai , Dorjoy Chowdhury Cc: linux-fsdevel@vger.kernel.org, Linus Torvalds , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, ceph-devel@vger.kernel.org, gfs2@lists.linux.dev, linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org, v9fs@lists.linux.dev, linux-kselftest@vger.kernel.org, viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, chuck.lever@oracle.com, alex.aring@gmail.com, arnd@arndb.de, adilger@dilger.ca, mjguzik@gmail.com, smfrench@gmail.com, richard.henderson@linaro.org, mattst88@gmail.com, linmag7@gmail.com, tsbogend@alpha.franken.de, James.Bottomley@hansenpartnership.com, deller@gmx.de, davem@davemloft.net, andreas@gaisler.com, idryomov@gmail.com, amarkuze@redhat.com, slava@dubeyko.com, agruenba@redhat.com, trondmy@kernel.org, anna@kernel.org, sfrench@samba.org, pc@manguebit.org, ronniesahlberg@gmail.com, sprasad@microsoft.com, tom@talpey.com, bharathsm@microsoft.com, shuah@kernel.org, miklos@szeredi.hu, hansg@kernel.org Date: Thu, 16 Apr 2026 06:28:09 -0700 In-Reply-To: <2026-04-16-raunchy-random-curfew-guide-GmtLJR@cyphar.com> References: <20260328172314.45807-1-dorjoychy111@gmail.com> <20260328172314.45807-2-dorjoychy111@gmail.com> <2026-04-16-selfless-milky-wasps-shin-p6liRL@cyphar.com> <2026-04-16-raunchy-random-curfew-guide-GmtLJR@cyphar.com> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV 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Thu, 2026-04-16 at 23:05 +1000, Aleksa Sarai wrote: > On 2026-04-16, Dorjoy Chowdhury wrote: > > On Thu, Apr 16, 2026 at 5:41=E2=80=AFPM Aleksa Sarai wrote: > > >=20 > > > On 2026-03-28, Dorjoy Chowdhury wrote: > > > > This flag indicates the path should be opened if it's a regular fil= e. > > > > This is useful to write secure programs that want to avoid being > > > > tricked into opening device nodes with special semantics while thin= king > > > > they operate on regular files. This is a requested feature from the > > > > uapi-group[1]. > > > >=20 > > > > A corresponding error code EFTYPE has been introduced. For example,= if > > > > openat2 is called on path /dev/null with OPENAT2_REGULAR in the fla= g > > > > param, it will return -EFTYPE. EFTYPE is already used in BSD system= s > > > > like FreeBSD, macOS. > > > >=20 > > > > When used in combination with O_CREAT, either the regular file is > > > > created, or if the path already exists, it is opened if it's a regu= lar > > > > file. Otherwise, -EFTYPE is returned. > > > >=20 > > > > When OPENAT2_REGULAR is combined with O_DIRECTORY, -EINVAL is retur= ned > > > > as it doesn't make sense to open a path that is both a directory an= d a > > > > regular file. > > > >=20 > > > > [1]: https://uapi-group.org/kernel-features/#ability-to-only-open-r= egular-files > > > >=20 > > > > Signed-off-by: Dorjoy Chowdhury > > > > --- > > >=20 > > > Aside from the nit below, feel free to take a > > >=20 > > > Reviewed-by: Aleksa Sarai > > >=20 > >=20 > > Thanks for reviewing! > >=20 > > > > diff --git a/fs/open.c b/fs/open.c > > > > index 681d405bc61e..a6f445f72181 100644 > > > > --- a/fs/open.c > > > > +++ b/fs/open.c > > > > @@ -960,7 +960,7 @@ static int do_dentry_open(struct file *f, > > > > if (f->f_mapping->a_ops && f->f_mapping->a_ops->direct_IO) > > > > f->f_mode |=3D FMODE_CAN_ODIRECT; > > > >=20 > > > > - f->f_flags &=3D ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC); > > > > + f->f_flags &=3D ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC | OPE= NAT2_REGULAR); > > >=20 > > > It's not clear to me why you dropped this, I didn't see a review > > > mentioning it either. (General note: Ideally the cover letter changel= og > > > would mention who suggested a change in brackets after the changelog > > > line so it's easier to track where a change might've come from.) > > >=20 > >=20 > > Thanks for the general note. I will keep that in mind. > >=20 > > The review was from Jeff Layton in v5 > > https://lore.kernel.org/linux-fsdevel/5fcc2a6e6d92dae0601c6b3b8faa8b2f8= 3981afb.camel@kernel.org/ > > " 1. OPENAT2_REGULAR leaks into f_flags - do_dentry_open() strips > > open-time-only flags (O_CREAT|O_EXCL|O_NOCTTY|O_TRUNC) > > but does not strip OPENAT2_REGULAR. When a regular file is > > successfully opened via openat2() with this flag, the bit > > persists in file->f_flags and will be returned by fcntl(fd, F_GETFL).= " > >=20 > > I think it makes sense to strip off as OPENAT2_REGULAR is an open time > > only flag (like O_CREAT and the others already), right? >=20 > Well, O_DIRECTORY isn't stripped so if we want to mirror that behaviour > then it shouldn't be stripped either IMHO. >=20 > O_NOCTTY and O_TRUNC make sense to strip (they are not relevant to the > file after it was opened -- truncation only happens at open time and you > can always set your controlling TTY later). >=20 > The story with O_CREAT and O_EXCL is a bit more complicated. They are > stripped but the history there is unclear -- the line was added in Linux > 0.98.4(!) with no mention in the release note at the time. (Linus: I > wonder if you remember why this was changed at the time? Sorry for the > trip down memory lane...) >=20 > However, the existence of F_CREATED_QUERY kind of shows that these kinds > of checks are stuff that userspace can find handy (though FMODE_CREATED > is more useful than O_CREAT|O_EXCL anyway). O_EXCL is used internally > for stuff so it can be re-exposed, I'm just not sure it's a good > precedent to make a decision based on. >=20 > Then again, userspace can check with fstat(2) so it's not the end of the > world, but I don't really see a strong reason to hide information from > userspace. Since the mail was from Claude (and it tends to give silly > nits like that) I'm not sure whether Jeff would agree with my view or > not. I don't have a strong feeling either way, but it "feels" like O_REGULAR is not particularly useful to return in F_GETFL. Once the file is open, then O_REGULAR really doesn't matter anymore. We _know_ it's a regular file at that point or the open wouldn't have happened. F_GETFL is more useful for showing flags that actually affect how the file description works (e.g. O_DIRECT, O_ASYNC, etc.). --=20 Jeff Layton