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[80.187.86.54]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4bb55af2901sm57437255e9.13.2026.11.13.04.37.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Nov 2026 04:37:02 -0800 (PST) Message-ID: Subject: Re: [PATCH RFC 39/41] usb: gadget: f_mass_storage: refuse files on pseudo filesystems 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 13:36:59 +0100 In-Reply-To: <20261110-work-loop-pseudo-v1-39-4c998976c6c7@kernel.org> References: <20261110-work-loop-pseudo-v1-0-4c998976c6c7@kernel.org> <20261110-work-loop-pseudo-v1-39-4c998976c6c7@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: > fsg_lun_open() takes any regular file as the backing file of a LUN. > The > file-storage kthread then reads and writes it with kernel_read() and > kernel_write() on behalf of the USB host. With a procfs or sysfs file > behind a LUN the host gets to read and write kernel interfaces with > kernel credentials. Refuse files on pseudo filesystems just like loop > does. >=20 > Signed-off-by: Christian Brauner (Amutable) Reviewed-by: Alexander Mikhalitsyn > --- > =C2=A0drivers/usb/gadget/function/storage_common.c | 5 +++++ > =C2=A01 file changed, 5 insertions(+) >=20 > diff --git a/drivers/usb/gadget/function/storage_common.c > b/drivers/usb/gadget/function/storage_common.c > index 75831f2c7abe..83683ade20c2 100644 > --- a/drivers/usb/gadget/function/storage_common.c > +++ b/drivers/usb/gadget/function/storage_common.c > @@ -211,6 +211,11 @@ int fsg_lun_open(struct fsg_lun *curlun, const > char *filename) > =C2=A0 goto out; > =C2=A0 } > =C2=A0 > + if (file_is_pseudo(filp)) { > + LINFO(curlun, "file on a pseudo filesystem: %s\n", > filename); > + goto out; > + } > + > =C2=A0 /* > =C2=A0 * If we can't read the file, it's no good. > =C2=A0 * If we can't write the file, use it read-only.