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([2401:4900:78f2:772b:141e:4f0f:8f8f:6f84]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-29498d4254asm128996765ad.82.2025.10.28.13.03.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Oct 2025 13:03:28 -0700 (PDT) From: Brajesh Patil To: miklos@szeredi.hu, stefanha@redhat.com, vgoyal@redhat.com, eperezma@redhat.com Cc: virtualization@lists.linux.dev, virtio-fs@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, skhan@linuxfoundation.org, linux-kernel-mentees@lists.linux.dev, david.hunter.linux@gmail.com, khalid@kernel.org, Brajesh Patil Subject: [PATCH] fuse: virtio_fs: add checks for FUSE protocol compliance Date: Wed, 29 Oct 2025 01:33:11 +0530 Message-ID: <20251028200311.40372-1-brajeshpatil11@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel-mentees@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Add validation in virtio-fs to ensure the server follows the FUSE protocol for response headers, addressing the existing TODO for verifying protocol compliance. Add checks for fuse_out_header to verify: - oh->unique matches req->in.h.unique - FUSE_INT_REQ_BIT is not set - error codes are valid - oh->len does not exceed the expected size Signed-off-by: Brajesh Patil --- fs/fuse/virtio_fs.c | 30 +++++++++++++++++++++++++----- 1 file changed, 25 insertions(+), 5 deletions(-) diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c index 6bc7c97b017d..52e8338bf436 100644 --- a/fs/fuse/virtio_fs.c +++ b/fs/fuse/virtio_fs.c @@ -764,14 +764,34 @@ static void virtio_fs_request_complete(struct fuse_req *req, { struct fuse_args *args; struct fuse_args_pages *ap; - unsigned int len, i, thislen; + struct fuse_out_header *oh; + unsigned int len, i, thislen, expected_len = 0; struct folio *folio; - /* - * TODO verify that server properly follows FUSE protocol - * (oh.uniq, oh.len) - */ + oh = &req->out.h; + + if (oh->unique == 0) + pr_warn_once("notify through fuse-virtio-fs not supported"); + + if ((oh->unique & ~FUSE_INT_REQ_BIT) != req->in.h.unique) + pr_warn_ratelimited("virtio-fs: unique mismatch, expected: %llu got %llu\n", + req->in.h.unique, oh->unique & ~FUSE_INT_REQ_BIT); + + WARN_ON_ONCE(oh->unique & FUSE_INT_REQ_BIT); + + if (oh->error <= -ERESTARTSYS || oh->error > 0) + pr_warn_ratelimited("virtio-fs: invalid error code from server: %d\n", + oh->error); + args = req->args; + + for (i = 0; i < args->out_numargs; i++) + expected_len += args->out_args[i].size; + + if (oh->len > sizeof(*oh) + expected_len) + pr_warn("FUSE reply too long! got=%u expected<=%u\n", + oh->len, (unsigned int)(sizeof(*oh) + expected_len)); + copy_args_from_argbuf(args, req); if (args->out_pages && args->page_zeroing) { -- 2.43.0