From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0E1FA4A3F27; Tue, 15 Sep 2026 11:33:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789472038; cv=none; b=Qhtnx6/bgiWXVH/bgqsohVTscBDSnE07nrLKMGlLxSAZB2Uy4sDt4WFs/ogA6xinqxw0s5tlxc/E1trfJeJ5v+hWbOMMHMfaOsf45w0CEPU0vJ3oQH1iYZs7M8yKzRaf4I/gp3kzkvx9V15yUwVoClpCPH6thfy5BUJphBp8K+0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789472038; c=relaxed/simple; bh=G9FG2jHFipdUrRTGsnorEbb5m5RZUr4ZNfIJ8EYrZNY=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=pKzAvRdegU/AQR+LwwuRPcMxPs8ohHMqR2JcGW4ekmzFMfViRg7PaZq0DsfaCPGbUlj+MqfcxYUWYFVoRl24VcFZOT/TT5/0B5h84rxPPer4pUxT8qXr9212qRziCydHjsKQagVD2zIcIV9jjsfCmphtUQkQtqo5Q5wTO4oD5vA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KlpWXuFj; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="KlpWXuFj" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E01081F000FF; Tue, 15 Sep 2026 11:33:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789472034; bh=mbTaUTx0F+8Yd8wvmtUsGd49oHWKxWwv7CwFTyLjhec=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=KlpWXuFj0+jdehVdQRW9dTm9BsasJoCQHq4y714jucc2LKezn+Raj3o0ioX232wqM jhHvMuhWUpiDNoQEY8ZOItiHHjXIh3EJ4lYCmA5rI9RGISwFKPW38moaoO3+dsZ0aK HShijMbdV4vAKfbEdZN7JwWHJCH9KbWrPxcDpTVAS0WUv3FhYQrUmcvC9ARRSnSa7u Ca768uVHlWEAIo6sTG8e8Q1xpvU8CLuiq6NSrBvgzzER0wYqMt62L865asuebsmyIW I7PEM9/+fxn9Mvp/KBLnfVW338UGGCg59dyrovq5duqMA/k5+J43h20hfjg0v7DEBj Nim9gww77JPsw== From: Christian Brauner Date: Tue, 15 Sep 2026 13:31:06 +0200 Subject: [PATCH RFC POC 20/50] file: warn when the descriptor table is unshared with slots Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260915-work-fd-reserve-unify-folded-v1-20-4d5217d6b246@kernel.org> References: <20260915-work-fd-reserve-unify-folded-v1-0-4d5217d6b246@kernel.org> In-Reply-To: <20260915-work-fd-reserve-unify-folded-v1-0-4d5217d6b246@kernel.org> To: Linus Torvalds Cc: Alexander Viro , Jann Horn , Jan Kara , Ingo Molnar , Peter Zijlstra , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Oleg Nesterov , linux-alpha@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-openrisc@vger.kernel.org, linux-parisc@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, Jens Axboe , io-uring@vger.kernel.org, netdev@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-gpio@vger.kernel.org, linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org, bpf@vger.kernel.org, David Airlie , virtualization@lists.linux.dev, kvm@vger.kernel.org, kexec@lists.infradead.org, linux-hyperv@vger.kernel.org, "Christian Brauner (Amutable)" X-Mailer: b4 0.17-dev-db0b7 X-Developer-Signature: v=1; a=openpgp-sha256; l=1273; i=brauner@kernel.org; h=from:subject:message-id; bh=G9FG2jHFipdUrRTGsnorEbb5m5RZUr4ZNfIJ8EYrZNY=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWSt1Klt0PSve+Zwt2WPgtbjy2r2c+q+Ga6c6JRtXJz8V 7d7s9uBjlIWBjEuBlkxRRaHdpNwueU8FZuNMjVg5rAygQxh4OIUgIkk9TEybK8Ujbgr9+l9SPar Xzk+r7k8K/PX8z83lr3l0RmsOXPvPIb/xe7Pwk1X1l5rbbs/0/NrxfS1XTYnq53m69hY7lW8vLu CBQA= X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 If the fdtable is unshared or the task exits we can't install reservations. The reserved fd isn't reserved anymore. execve() would leak the reservation into the child. Signed-off-by: Christian Brauner (Amutable) --- fs/exec.c | 3 +++ kernel/fork.c | 2 ++ 2 files changed, 5 insertions(+) diff --git a/fs/exec.c b/fs/exec.c index 745f6eb5279e..1aa0f7b99fc3 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1159,6 +1159,9 @@ int begin_new_exec(struct linux_binprm * bprm) */ io_uring_task_cancel(); + /* A prepared descriptor would be installed into the new program. */ + VFS_WARN_ON_ONCE(me->fd_slots.nr); + /* Ensure the files table is not shared. */ retval = unshare_files(); if (retval) diff --git a/kernel/fork.c b/kernel/fork.c index 59c5cfa3e482..bd0e1e85abb0 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -3217,6 +3217,8 @@ static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp if ((unshare_flags & CLONE_FILES) && (fd && atomic_read(&fd->count) > 1)) { + /* Prepared descriptors live in the table we are about to leave. */ + VFS_WARN_ON_ONCE(current->fd_slots.nr); fd = dup_fd(fd, NULL); if (IS_ERR(fd)) return PTR_ERR(fd); -- 2.53.0