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=1794340259; b=Ka8lLfbOFLRl9mfb8nB/8xLV5cfal+/W09673HyOkBrGmNDxfREm3SREtv6cUM6pQyJI 9nximgNc547carCeQC1sBtufu3wsZ6VpgKPq05T5E0ZVBdCSHEPtUodYjcoI6Xnb6gQAR LtY4wSNZhzkH6UuUXmy72m02ztn7cY/do1nNq6TKOoQGurU0yPgyws3fPu6IOp00iE/U6 pmzknl2tmgGbfmZkPdlQWBCqJrilJG8OtH2JuBBj5+Ko6lJ4uZ/ZUvmQ3wHVIeTG/S+Op GgyUschn5fVFYGtmKPSfBuXAID6hudIN281ptKql60ZrcKz0ldbM9yAxS9NynRM0WCQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794340259; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=pEVjulOGJkpyWrsEyn3njWgpdgVbGI+AU5xIIwfRk+s=; b=Df2nONhIWNrU59j1+MzW6GQLsGatDh+Y01yLYVlsz/jRQqYUSvHMk2+1qClqN+gaLFP+ +zRgX0hJNmC0ITGEnFQqtYHQwUO1/dqSzQ2Vx3ArVmnWYR3NWZEdnb2Nn2jRptJTxs2X6 F3GIEa85kq3x5SfNf44My4k8R781IFv0QM0Zhau07vZJd9SqixLTX3bWR9bsdHu6/Pucy cFVJrf9NVJClgzxsLrbSajbuqvZWLxj/DeDsKVQi6w9Z0mi/s+CvFBi+vDU4P00ESoJRP 6OzV2OPEkQ+fi2eEWZtwrL64+IFbc8532m+PhNFL+cKfquUlCGq4CYMqIAU5Oxg1rtg== 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=TuzXRpMy; 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 BCBFF606A320 for ; Tue, 10 Nov 2026 19:50:58 +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=TuzXRpMy Received: by smtp.kernel.org (Postfix) with ESMTPSA id BDE9A1F0089F; Tue, 10 Nov 2026 19:50:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794340258; bh=pEVjulOGJkpyWrsEyn3njWgpdgVbGI+AU5xIIwfRk+s=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=TuzXRpMyDRCx3vFiV9RgKNQsH0Vdu5Aob+sE97AABeGzRTlWu8dUNl78yjery2OGP TwHhBj96/YxjVNtGNvjhNQrhb3vSRU/nD//xdeG0/21zttnn3cdRmy6LtzbNRZG5pz D5U7UcYJtKKz9rS3Gsxkpgx6YApXDfaOs7KPRE0VqHpUdJhQ3ZvEAQGnnMjepYvtBd TyfajSqUVu2xGWZHAx4IVTwkfwUAgdBeGJXd/xdiD/ED8NRS0XzWZFP9d395zn/AOS AJFvQarP3XxBsfWiJ3pE6NIoa2JNT7/1UxLjgwFwzz0Bf/YB8FDXa1nCTiyPfyzccd 4A/M6z97+7erg== From: Sasha Levin To: stable@vger.kernel.org Cc: Sung Byeongchan , Miklos Szeredi , Sasha Levin Subject: [PATCH 5.15.y 2/2] virtiofs: validate fixed-output response length Date: Tue, 10 Nov 2026 14:50:54 -0500 Message-ID: <20261110194003.3568480-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261110194003.3568480-1-sashal@kernel.org> References: <20261107060741-failed-5.15-5364d081125a@kernel.org> <20261110194003.3568480-1-sashal@kernel.org> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Sung Byeongchan [ Upstream commit 5364d081125a34e90851fbb46ecc93f79339ce78 ] A short successful virtiofs response can leave the fixed-output portion of the request argument buffer unwritten. The completion path nevertheless copies the full declared output to the request destination, allowing stale allocator contents to reach callers such as fuse_statfs(). Require successful fixed-output responses to contain their complete declared output. Continue to permit a shorter final argument only for out_argvar requests. Reject positive and internal restart error values and require valid error replies to be header-only. The error already stored in the FUSE output header is returned by fuse_request_end(), so do not copy output arguments from an error reply. This was found by source review with AI assistance. A header-only successful FUSE_STATFS reply returned stale fields in nine of nine calls across three boots. The fixed kernel rejected the short response and preserved complete replies, valid negative-error replies, and variable-output replies. Fixes: a62a8ef9d97d ("virtio-fs: add virtiofs filesystem") Cc: stable@vger.kernel.org Assisted-by: LLM Signed-off-by: Sung Byeongchan Signed-off-by: Miklos Szeredi Signed-off-by: Sasha Levin --- fs/fuse/virtio_fs.c | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c index c375a5f001056..14c1ae5075938 100644 --- a/fs/fuse/virtio_fs.c +++ b/fs/fuse/virtio_fs.c @@ -522,6 +522,10 @@ static void copy_args_from_argbuf(struct fuse_args *args, struct fuse_req *req) unsigned int num_out; unsigned int i; + /* fuse_request_end() returns this error; there are no args to copy. */ + if (req->out.h.error) + goto out; + remaining = req->out.h.len - sizeof(req->out.h); num_in = args->in_numargs - args->in_pages; num_out = args->out_numargs - args->out_pages; @@ -547,6 +551,7 @@ static void copy_args_from_argbuf(struct fuse_args *args, struct fuse_req *req) if (args->out_argvar) args->out_args[args->out_numargs - 1].size = remaining; +out: kfree(req->argbuf); req->argbuf = NULL; } @@ -554,7 +559,9 @@ static void copy_args_from_argbuf(struct fuse_args *args, struct fuse_req *req) /* Verify that the server properly follows the FUSE protocol */ static bool virtio_fs_verify_response(struct fuse_req *req, unsigned int len) { + struct fuse_args *args = req->args; struct fuse_out_header *oh = &req->out.h; + unsigned int expected; if (len < sizeof(*oh)) { pr_warn("virtio-fs: response too short (%u)\n", len); @@ -569,6 +576,29 @@ static bool virtio_fs_verify_response(struct fuse_req *req, unsigned int len) oh->unique, req->in.h.unique); return false; } + if (oh->error <= -ERESTARTSYS || oh->error > 0) { + pr_warn("virtio-fs: invalid error value (%d)\n", oh->error); + return false; + } + + if (oh->error) { + if (len != sizeof(*oh)) { + pr_warn("virtio-fs: error response too long (%u)\n", len); + return false; + } + return true; + } + + expected = sizeof(*oh) + + fuse_len_args(args->out_numargs, args->out_args); + if (len > expected || + (len < expected && + (!args->out_argvar || + expected - len > args->out_args[args->out_numargs - 1].size))) { + pr_warn("virtio-fs: invalid response length (%u, expected %u)\n", + len, expected); + return false; + } return true; } -- 2.53.0