From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794302425; b=XJv75ARIlNdgk0M2nJtnvqtYw6+h/2qRS/vV9B8PcHqO5ob0eRfIgFjcHdOJ40pi6Sgu su7oYsRP8cTwaSO/ZvVraJYrMQWSYsqqDtaPXJ4t5daL+PFK7FnBMjI8uLLJLyziO0prl yXzcvXlMH6P1+BtTycVWP4OwtaBGxJ8GxGfj7UXIk8a18q0vkieu95jVZJotkdfsiKVAB hcIRR+U0pbcWhmFNhMoZp5eFyt0F5N0jkGLE8nxuP3wistfmt7Al6KzqT0w2W2DcUmIbK YRejg7HE/u8ir8DtxHobeZMt8yr6wFghlynemb5S2cReRIKv4oPKwQFAsKF+lkdM54g== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794302425; h=Received:DKIM-Signature:From:Date:Subject:MIME-Version:Content-Type: Content-Transfer-Encoding:Message-Id:References:In-Reply-To:To:Cc: X-Mailer:X-Developer-Signature:X-Developer-Key; bh=5v6oTkZQz6qlfBhdJSuXnvnO8rYqx/rzC+7+Nl5/OGM=; b=iD08AoSh0gQECC1jh9zW9fpnu19dtOX9V4wVeEXGCUSP4M4KOU8/4veQC3dVeDheeIsv vEBdcqaTziZBI8BaXFq/IyKsX50H/wqjG7j15sN/joUkwTx9ZmlwQ1gdP+LxmGAgTUJ+Y mwFaQa/jhnfdWmEEnzfAI1gSvqhcUb3yodGApQtex3jSUZsnLgj4D7EL0tWo2PDtNgJaW 5sfd2U1dAPtEcqjMVwHrWinI0rMtunSVKFE9TiPv5hQ0KO9dJpRqxcUhqBr6yClLcA2Ah HepyCzCE1vmVOzFAnlljfHj/3qalIOJVJXzgOyUr672hZl+R1ApK2hEei4luKhKMGWQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=eIJ0bZ6Y; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1124D606DABA; Tue, 10 Nov 2026 09:20:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=eIJ0bZ6Y Received: by smtp.kernel.org (Postfix) with ESMTPSA id 515E81F0089F; Tue, 10 Nov 2026 09:20:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794302424; bh=5v6oTkZQz6qlfBhdJSuXnvnO8rYqx/rzC+7+Nl5/OGM=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=eIJ0bZ6YykzyfYaq0uQnsLuPNj+m0vg4MOIRUUV7WyIHrzOWlMn5BpzKyvQO1xQnK lIgHxLYXr0xM6gXAPduca8fCpGnrbXmRu3n7sX++lmrPokRdnMxOQCvAaieuNDey1/ rDMY2lnbcyTg88AQ5EnW+l0uOlH6KcCfGavMFZPvkrzrCwVDMo4o1H9usL4RbMeid9 8ju7v6AtrNpyzqVV8uy5DYhL2Vr+eLE/ymRsWc8pcaS97R4A8Z95dfIgLeSJCXVpWi mDeT0clD8WfcFmQfLKdl3Rcurbo/W+eyqIPzNmzhefzjE4bnqF8y5kxjx80v9c4Gko v/as+SN9c7AFA== From: Christian Brauner Date: Tue, 10 Nov 2026 10:14:55 +0100 Subject: [PATCH RFC 39/41] usb: gadget: f_mass_storage: refuse files on pseudo filesystems 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 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261110-work-loop-pseudo-v1-39-4c998976c6c7@kernel.org> References: <20261110-work-loop-pseudo-v1-0-4c998976c6c7@kernel.org> In-Reply-To: <20261110-work-loop-pseudo-v1-0-4c998976c6c7@kernel.org> To: 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, "Christian Brauner (Amutable)" X-Mailer: b4 0.17-dev-ce4c1 X-Developer-Signature: v=1; a=openpgp-sha256; l=1124; i=brauner@kernel.org; h=from:subject:message-id; bh=5CZmEVUvUM8phb7GCUC0PbdIONUtutPPh5jN88b8MUg=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWR9enDwpOymfbk/lix9c8OUO8H7nMDJjqNuYfXt8RN5b SZ7VM/p6yhlYRDjYpAVU2RxaDcJl1vOU7HZKFMDZg4rE8gQBi5OAZhIsgXDP81qmQUMxt7JIhtj H769H+D76yOfp7vrv8Uv+XNqFL+3cjL8szGK7szT6zNcPi0pgC3zv/C19XHNGld3L/vwMHyKxLW bjAA= X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 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. Signed-off-by: Christian Brauner (Amutable) --- drivers/usb/gadget/function/storage_common.c | 5 +++++ 1 file changed, 5 insertions(+) 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) goto out; } + if (file_is_pseudo(filp)) { + LINFO(curlun, "file on a pseudo filesystem: %s\n", filename); + goto out; + } + /* * If we can't read the file, it's no good. * If we can't write the file, use it read-only. -- 2.53.0