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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-Archived-By: 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 X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Rspamd-Server: rspam09 X-Stat-Signature: ygkwby15r7o1ks1kjpsfscup3x68apti X-Rspamd-Queue-Id: 5A7DE160004 X-Rspam-User: X-HE-Tag: 1794302425-867888 X-HE-Meta: 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 8tSve+61 7xpHf8s995MiY0A2humO6UfoMmc/YVkRRE/Y8ODVGfGu5l+zb7HeR8Xn+h5wObeuRRGuX2RUPo2HeK4z+f0VkAFAlXCCitnFan3cG84aTLV1DZcALWr222G6VCW5xVc4HZ8LmPt/tRtFDAQ5Vwh0GnQL0z42C1Y7YQSG/wCrmfN4I7gZvr/QyIurlItWFmhpMwOq0uzycNtLp+yad8Ky7bhuUinOpL49ZMxFCP2wXl6TDjSkrn4eLHQ//iOaCae0sq6nw1YzUlXJJaZjAYC6v4P/GtAUuBXX402Dq Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 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