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[80.187.86.54]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4bb56680ea9sm31982365e9.0.2026.11.13.02.15.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Nov 2026 02:15:16 -0800 (PST) Message-ID: Subject: Re: [PATCH RFC 33/41] fs: add file_is_pseudo() From: Alexander Mikhalitsyn To: Christian Brauner , linux-fsdevel@vger.kernel.org Cc: Jann Horn , Chris Mason , Josef Bacik , Christoph Hellwig , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, Alexander Viro , Jan Kara , linux-scsi@vger.kernel.org, target-devel@vger.kernel.org, driver-core@lists.linux.dev, linux-mm@kvack.org, bpf@vger.kernel.org, linux-security-module@vger.kernel.org, selinux@vger.kernel.org, apparmor@lists.ubuntu.com, linux-nfs@vger.kernel.org, netdev@vger.kernel.org, fuse-devel@lists.linux.dev, linux-efi@vger.kernel.org, xen-devel@lists.xenproject.org, ocfs2-devel@lists.linux.dev, linux-s390@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-usb@vger.kernel.org, Amir Goldstein , linux-erofs@lists.ozlabs.org, linux-kselftest@vger.kernel.org Date: Fri, 13 Nov 2026 11:15:14 +0100 In-Reply-To: <20261110-work-loop-pseudo-v1-33-4c998976c6c7@kernel.org> References: <20261110-work-loop-pseudo-v1-0-4c998976c6c7@kernel.org> <20261110-work-loop-pseudo-v1-33-4c998976c6c7@kernel.org> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2-0+deb13u1 X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 On Tue, 2026-11-10 at 10:14 +0100, Christian Brauner wrote: > Add a helper to check whether a file is a regular file on a pseudo > filesystem. Only regular files count. Device nodes on pseudo > filesystems > such as devpts, binderfs or the block devices on bdevfs are what they > are. >=20 > Look at the inode that actually provides the data via d_real_inode(). > overlayfs accepts sysfs, cgroup2, debugfs, tracefs, configfs and > securityfs as lower layers and reads of such an overlayfs file are > served by the file on the pseudo filesystem. Checking the overlayfs > inode would miss that. >=20 > No functional changes. >=20 > Signed-off-by: Christian Brauner (Amutable) Reviewed-by: Alexander Mikhalitsyn > --- > =C2=A0include/linux/fs.h | 12 ++++++++++++ > =C2=A01 file changed, 12 insertions(+) >=20 > diff --git a/include/linux/fs.h b/include/linux/fs.h > index 99caef43ff3c..407ffb6342ec 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -2553,6 +2553,18 @@ static inline const struct inode > *file_user_inode(const struct file *f) > =C2=A0 return file_inode(f); > =C2=A0} > =C2=A0 > +/* > + * Regular files on pseudo filesystems are kernel interfaces and > must not be > + * used as storage. Look through stacking filesystems at the inode > that > + * provides the data. > + */ > +static inline bool file_is_pseudo(const struct file *file) > +{ > + const struct inode *inode =3D d_real_inode(file- > >f_path.dentry); > + > + return S_ISREG(inode->i_mode) && (inode->i_sb->s_iflags & > SB_I_PSEUDO); > +} > + > =C2=A0static inline struct file *file_clone_open(struct file *file) > =C2=A0{ > =C2=A0 return dentry_open(&file->f_path, file->f_flags, file- > >f_cred);