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=1794336947; b=SJTHYjYExrQzUxaXiy6nHogmdIEV6SurJz5VAmcVCawA38yCcQoOSIXPI5YiFBU/4S14 w7vETQQCU2HAbxiDWL7479lrg7KEkNCpjKY9/OJ+/rzLHjtj7O02XB+vXraDzud9+bdu2 X9wPey+hWliMOGfxBYsW7WK3CAXoqnXtF4GZ1bnPkJKiguR6z3u32MF3XpvKH81cqM2Az UYwXf0CWR2HH5aQViyiFRKj7ayfFIv7TwbQTw2rABvuUXS4t6Igu1L6qCuEk0e7sxzv3u vISQtIydgAvoCkoKhm1HRxHErdHHA+PVChxf0KbZmbDdp8uM04bfG9JBtmai9W9/3IA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794336947; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=ICzbR2U37r15UfaahFqG0D4NcQ52MDEDvf1e+u1bKkQ=; b=5pmYdYoXgWpul8kXEjP24rdzLAQkbr6vxFY3XF8thSTlpEwriKdE8wrCZdU/dNvoj9o+ xCnOxuBFpalbn7ph2vKBKASMPOleuCBYx77e9vopndhrUZbmsA0onO/fpF/KSoFuU/IJM 9bhM1djJHkHYaES7jiHaI8O9G021/oISSAIWRRY1Vno5QPzeRsNlBEEx/QjLNSNaJZ1o3 8I8Dr2PfDo4kTB5ZMU7K1WaS9N75WV5IeLhh7Twc0AI+ImRxyJ/uC24GTGGOyoycirg8K Eo2QW9Lf56InZyB7mddhwM4x29+9/SRnBIVDASmPFzFkFE/mSxDuSpOrcDNwQpFD0Vw== 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=KMGpf45D; 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 20219606A325 for ; Tue, 10 Nov 2026 18:55:47 +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=KMGpf45D Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6809B1F008A3; Tue, 10 Nov 2026 18:55:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794336947; bh=ICzbR2U37r15UfaahFqG0D4NcQ52MDEDvf1e+u1bKkQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=KMGpf45DY3ODdBZIVRmqjFZrrjVOVQm7qTYtHfQPURwhLH/WKbubWDnO3GPIAIk+z tAD1ncv/eyF+Tz5W+IOVWOdWGUgF8VWP+Mb3W4HHz44rhlvJURxHAujVYywqKQbWyu KVU3MJxZPAIi/IKqJjiadLra4c8LpNbdOBlzhjbbk8S0hCkQUWM1VESExuFhZXcooJ bqAygB9u2x5OJ818RXUnHjYvKnAipDzxSdvtylChdPNcYGC113ccJSLpegK8hTlRP6 F10/GEwPUnp6mjrZ5V8Q5DC/YqL1HrDbQXWwYsotRXsqE0Ph7CyeKGC5P+rH+mIvvo sn7OCpL524elg== From: Sasha Levin To: stable@vger.kernel.org Cc: Sung Byeongchan , Miklos Szeredi , Sasha Levin Subject: [PATCH 6.6.y 2/2] virtiofs: validate fixed-output response length Date: Tue, 10 Nov 2026 13:55:44 -0500 Message-ID: <20261110184424.3240758-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261110184424.3240758-1-sashal@kernel.org> References: <20261107053609-failed-6.6-5364d081125a@kernel.org> <20261110184424.3240758-1-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 7b1e9291c3ef4..b5ecbd146301b 100644 --- a/fs/fuse/virtio_fs.c +++ b/fs/fuse/virtio_fs.c @@ -535,6 +535,10 @@ 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; @@ -560,6 +564,7 @@ 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; } @@ -567,7 +572,9 @@ 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); @@ -582,6 +589,29 @@ 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