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 A723E4E36F3; Wed, 30 Sep 2026 15:46:03 +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=1790783168; cv=none; b=nKTpdgwLwO6G50WexePePREGsKYNpc1IsIfVbmkr5dRqReehhxEDDaDtKVkQqNp7+ef6BBfehmcsPBws4OsmCRDzr+eu7/eH2na2T1pRhNzj9Dt4duZBbgrFG7bcVGlkzkN/grqQ5bjiJU8DQa7RiJMss229vicA0fVg3ebz8Qc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790783168; c=relaxed/simple; bh=5S2WoUoBL4PfS4eECf3soIGghJl9DgAKhYOUbkua+04=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ek0yyqxMj3cFT2yhJAURG4oOZJ3ZVHq+Ch9DLprcz1Wb5my1VqMec4L60p7y8/DN7pXoOyAIiTiV3B6HNB286Blo5kAY0BWZWPIhlkrjDInr8jcLcwtcNEWVIzKLQxlbb6RFkzcI6c5kb6YwmmB9ERKb/O0eG0aM9hQ9XVIXtt8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=cpXlB+uk; 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="cpXlB+uk" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6F8CA1F000FF; Wed, 30 Sep 2026 15:46:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790783163; bh=GnEh3BKI4SXsdQxtuM5tUg3VYynPraXMGYMRYEKjzeA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=cpXlB+ukY33pS6cdseJp51OoSxI2ZODMI6hPLeh6Ji+gjix6ZUjpg8ki0/IY+Plrd 2wXMTx3dNI94vCalxwEjyPfAzDGqi1GrLLypqgGvHkvg6NMTjsiNInOMACKxwWLb2e XabK5WIXoOz4Muk01rloLGWHNVUrzKPfMzrbY1sM= 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 5.10 300/595] exec: do_close_on_exec() before taking exec_update_lock Date: Wed, 30 Sep 2026 17:23:13 +0200 Message-ID: <20260930152354.142322702@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152347.700140858@linuxfoundation.org> References: <20260930152347.700140858@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.10-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 @@ -1268,6 +1268,20 @@ 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 visibile until then. This also enables the update * to be lockless. @@ -1315,14 +1329,6 @@ int begin_new_exec(struct linux_binprm * flush_thread(); me->personality &= ~bprm->per_clear; - /* - * 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;