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=1794049663; b=H7h/LTmx+nr9vuTB/WmYs0dj1ZUWm4yRogtnPQU5xR47JkS84E0DgyveTT1cLpZXl2iI wWJ5NTgyEDZ5kOTJorJYtrdTsspx07JS9mRaJNjIdswtRTn+DkABtke+zwdtT2Dui4eLG yEA0fkEFPL+/l30nHsmLWRMSi1nSp3EbcseiNgkmxWCZ6o7MeiCMkmC4fBtNQEYEKFMAp RZHCeh9JjfbyYQhkU/AqpXDlC2cnbB+jmK+Y9sEt52usmgiy+N0j/ENRGmicFhN/zMNsv 4U9IYdfTUbVC0JZ2UGZyg3iQRsOKI1lKeMXFPvWvDeNOxE+yGfvzEzXq4htGzdjyeOA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794049663; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=3ROsdahLuYeCrEsVJpRzhbAgOlTOumYECmpnOz7UJac=; b=gi+8nnpdLm5BX7s4y+Ar9bIPKEhuIysUMD0NbWJc0xrldqWqtUsJfWIx129kM4spA+V9 ZTy5PMFHIBVJKHn4Jno3SXpzqK18hQxf1SZv4GR0UlR0aaQrGC08Srwju8F/teUstF6rj 6cmbVvJjkMRCe3F8ELwsh8pYYyijfXLS6lHX3ihTm0p8ksysjSacBalayaN3/QMwW9t3Y Sybg50dJGz9OT6hbIyfSeDLG4vk1B35FdOaiSD9tYyK0tZbyiW0yO/QtU2kKZWp9vHn80 v8rT4qBJDfjwJAZrc6ogzlXVOT3t8PCItjwMDuyO5ALwZPs2dq5aWjncJDbTU8fOXBg== 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=TlP4SVLa; 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 371CA606A32F for ; Sat, 7 Nov 2026 11:07:43 +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=TlP4SVLa Received: by smtp.kernel.org (Postfix) with ESMTPSA id A6AC11F0089F; Sat, 7 Nov 2026 11:07:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794049663; bh=3ROsdahLuYeCrEsVJpRzhbAgOlTOumYECmpnOz7UJac=; h=From:To:Cc:Subject:Date; b=TlP4SVLao8HwUQh0uMrla9/4/60dntMcLWyjir4QoaWj2JS8qkt9aNZ81Uw+oF4NT j42EHqGvm2fyvXsSu5+mmDDVQx9Nqf29d7nyT/nigdNtW6PwLCOt7yMe9o9n26cZiC tflUXAlx34sVcwpmN98YxKXYkZr18IPdktbj4TIT14rbp3SM/VUM4fj6fSf5OQdrWY Y/wghMra/vODorKM4h7BXsW7KhMNqrK4vbBZXEEAIFJ0bTpziMmA4ebyrNY3pVUUSf bl0NYjTtplcUkStq2VwSjRuuh0oYWJhbbB9eNmi5Bs2CI6vtuPEPj/TMqa0fXeaC8D xndvZP/2EZVfQ== From: Sasha Levin To: tjdqudcks0424@naver.com, mszeredi@redhat.com Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] virtiofs: validate fixed-output response length" failed to apply to 5.15-stable tree Date: Sat, 7 Nov 2026 06:07:41 -0500 Message-ID: <20261107060741-failed-5.15-5364d081125a@kernel.org> X-Mailer: git-send-email 2.53.0 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-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x 5364d081125a34e90851fbb46ecc93f79339ce78 # git commit -s git send-email --to '' --in-reply-to '20261107060741-failed-5.15-5364d081125a@kernel.org' --subject-prefix 'PATCH 5.15.y' 'HEAD^..' Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From 5364d081125a34e90851fbb46ecc93f79339ce78 Mon Sep 17 00:00:00 2001 From: Sung Byeongchan Date: Wed, 7 Oct 2026 15:19:49 +0900 Subject: [PATCH] virtiofs: validate fixed-output response length 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 --- 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 674fd784cdb80..ba8d79c4bcac6 100644 --- a/fs/fuse/virtio_fs.c +++ b/fs/fuse/virtio_fs.c @@ -727,6 +727,10 @@ 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; @@ -752,6 +756,7 @@ 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; } @@ -759,7 +764,9 @@ 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); @@ -774,6 +781,29 @@ 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