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 939B34E3235; Thu, 17 Sep 2026 15:50:27 +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=1789660230; cv=none; b=VndwpuzCnOMIicG+8A6OiJaJlUb5OCxgZwwY0qHHv3dr+8NKGOA7gpW3Vr2LPzh76TrvL2146BX3jUoIe4owjHbngBhY/2ZaWDccewbrCJXJgcBsOe9h/LzyhKhWzhjVM4nqPgMQHqZTkBgVib6UbVXzPxnrqmyOzj1wYDHrkzE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789660230; c=relaxed/simple; bh=IuELrcT1YGS2gNScTRamnpEJB852pDVGsFWIt66Zk4g=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=HaweJkMdrevvbkvu69jogRbCSjFncRWz5wAMZXWy7JvPnPTeZ5SuHx7ELigC+Tlsr09PafCR4C6Mg25iv+Mhm+yB67yN4tCDlcHu9nBNHMWNx8Owk+zoHz5SUIrUBGXfary8qzSjAuXl/z7iil8y0Yh5zXdYd80/vhvL5IQSq6A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=LJ0nji4A; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="LJ0nji4A" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5475C1F00893; Thu, 17 Sep 2026 15:50:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789660226; bh=Hjm7gKwh8KcXjp5To/bDLcHSXYlGNh1yhaj9jlchB94=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=LJ0nji4ASjHXkftFioVqaCs/L7RsyGa5bTMrZB00TnvbIULK28qY3dQp9WuSDnjFa aVgmE8VjbRZCHeAtZrt1sAAMzipMQrGgAt8o7RCr2FmXXh7pFmcXkDQK7nHYuwHnv0 VssOFxUEGfPlcHX4ORPmjxCRtoAivghntroVZ5xY= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Benjamin Peterson , Jann Horn , Jan Kara , "Christian Brauner (Amutable)" Subject: [PATCH 7.2 521/733] exec: do_close_on_exec() before taking exec_update_lock Date: Thu, 17 Sep 2026 16:13:49 +0100 Message-ID: <20260917151405.144829622@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260917151350.597953846@linuxfoundation.org> References: <20260917151350.597953846@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jann Horn commit e780259b54e618ceb4763fbc21314acf3565e813 upstream. do_close_on_exec() currently happens while holding the exec_update_lock, which is used in a lot of places that access process state to synchronize access checks. I recently added another such use of exec_update_lock, causing a regression. do_close_on_exec() can block waiting for a reply from a filesystem. That means a hung filesystem can block codepaths that use exec_update_lock; and it also means that a FUSE filesystem which attempts to inspect the calling process can deadlock. To avoid such problems, move do_close_on_exec() before the exec_update_lock is taken, but after the FD table has been copied if necessary. I have looked through all the calls between the old and new position of the do_close_on_exec() call; there seems to be no file descriptor table access in between. Reported-by: Benjamin Peterson Closes: https://lore.kernel.org/r/f5e8166a-88be-46c5-8939-1e5227ffe4c2@app.fastmail.com Fixes: 6650527444da ("proc: protect ptrace_may_access() with exec_update_lock (part 1)") Cc: stable@vger.kernel.org Signed-off-by: Jann Horn Link: https://patch.msgid.link/20260907-cloexec-before-exec-update-lock-v1-1-8018c201a7df@google.com Tested-by: Benjamin Peterson Reviewed-by: Jan Kara Signed-off-by: Christian Brauner (Amutable) Signed-off-by: Greg Kroah-Hartman --- fs/exec.c | 22 ++++++++++++++-------- 1 file changed, 14 insertions(+), 8 deletions(-) --- a/fs/exec.c +++ b/fs/exec.c @@ -1150,6 +1150,20 @@ int begin_new_exec(struct linux_binprm * goto out; /* + * We have to apply CLOEXEC before we change whether the process is + * dumpable (in setup_new_exec) to avoid a race with a process in userspace + * trying to access the should-be-closed file descriptors of a process + * undergoing exec(2). + * + * This can block on filesystem ->flush() handlers, including waiting + * for FUSE daemons, so do it before exec_mmap takes the + * exec_update_lock. + * This must happen after the point of no return, and after unsharing + * the FD table. + */ + do_close_on_exec(me->files); + + /* * Must be called _before_ exec_mmap() as bprm->mm is * not visible until then. Doing it here also ensures * we don't race against replace_mm_exe_file(). @@ -1199,14 +1213,6 @@ int begin_new_exec(struct linux_binprm * clear_syscall_work_syscall_user_dispatch(me); - /* - * We have to apply CLOEXEC before we change whether the process is - * dumpable (in setup_new_exec) to avoid a race with a process in userspace - * trying to access the should-be-closed file descriptors of a process - * undergoing exec(2). - */ - do_close_on_exec(me->files); - if (bprm->secureexec) { /* Make sure parent cannot signal privileged process. */ me->pdeath_signal = 0;