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[80.187.86.54]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-49c5a32d336sm5077482f8f.0.2026.11.13.02.27.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Nov 2026 02:27:26 -0800 (PST) Message-ID: <0c109a58804a2d782e549af6ad13e89532d9f9d2.camel@amutable.com> Subject: Re: [PATCH RFC 40/41] erofs: refuse files on pseudo filesystems as backing files 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 11:27:24 +0100 In-Reply-To: <20261110-work-loop-pseudo-v1-40-4c998976c6c7@kernel.org> References: <20261110-work-loop-pseudo-v1-0-4c998976c6c7@kernel.org> <20261110-work-loop-pseudo-v1-40-4c998976c6c7@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-kernel@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: > File-backed mounts take any regular file as the image and the same > goes > for the extra devices of such a mount. erofs reads them with the > credentials of the mounter so this doesn't hand out anything the > mounter > couldn't read anyway. But files on pseudo filesystems aren't images. > Refuse them just like loop does. >=20 > Signed-off-by: Christian Brauner (Amutable) Reviewed-by: Alexander Mikhalitsyn > --- > =C2=A0fs/erofs/super.c | 6 +++++- > =C2=A01 file changed, 5 insertions(+), 1 deletion(-) >=20 > diff --git a/fs/erofs/super.c b/fs/erofs/super.c > index ce05557bd998..980d5fc2b576 100644 > --- a/fs/erofs/super.c > +++ b/fs/erofs/super.c > @@ -158,7 +158,8 @@ static int erofs_init_device(struct erofs_buf > *buf, struct super_block *sb, > =C2=A0 if (!erofs_is_fileio_mode(sbi)) { > =C2=A0 dif->dax_dev =3D > fs_dax_get_by_bdev(file_bdev(file), > =C2=A0 &dif->dax_part_off, NULL, > NULL); > - } else if (!S_ISREG(file_inode(file)->i_mode)) { > + } else if (!S_ISREG(file_inode(file)->i_mode) || > + =C2=A0=C2=A0 file_is_pseudo(file)) { > =C2=A0 fput(file); > =C2=A0 return -EINVAL; > =C2=A0 } > @@ -835,6 +836,9 @@ static int erofs_file_get_tree(struct fs_context > *fc) > =C2=A0{ > =C2=A0 struct erofs_sb_info *sbi =3D fc->s_fs_info; > =C2=A0 > + if (file_is_pseudo(sbi->dif0.file)) > + return invalfc(fc, "source is on a pseudo > filesystem"); > + > =C2=A0 if (!test_opt(&sbi->opt, SUPERBLOCK_SHARE)) > =C2=A0 return get_tree_nodev(fc, erofs_fc_fill_super); > =C2=A0