From patchwork Mon Mar 17 07:00:20 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jiri Slaby X-Patchwork-Id: 874690 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 BD6B321A458; Mon, 17 Mar 2025 07:00:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742194858; cv=none; b=G3ZnOMH9O5I7eGHpUqb5XzXunFb5xvnoYSb3aOrXl/hUJti+H5nK8rrAf8Cm131UcPfQvwz4jsNlMBQmClZBCF640++YHYsUNPLK9nDSMFiNiLKhikF6HYWcmZji3dGMMbJfsaGEUj33kSsa87foDcCL5wELmof5Au+zEGkRjWs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742194858; c=relaxed/simple; bh=heoyOrgbbFmz7nxxRN+z8nbd3qdiXGzHhNH5YXrgRyY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=IXnb9Mx+fR0LtjqOhC4lbGM3u1JC6wKGUcrUTrxw35h2W6sUIll0KeguGgYD904Wy4jsOfmsqNEQZI+8SFhUKVmChBTWKTrVp0x+dzXmsS1j1ry6CwJmjLbcEml0ITMCoiud+Ov3IhmmXUqi28cHkMU8K2+0flhS2TLciNYujYc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=eE0thvIf; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="eE0thvIf" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 30676C4CEF2; Mon, 17 Mar 2025 07:00:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1742194858; bh=heoyOrgbbFmz7nxxRN+z8nbd3qdiXGzHhNH5YXrgRyY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=eE0thvIfMROO0DH0N+yXkOIQeRWPWSXmtYGC4Iio3VcN3nAQ2lPw9EcsLN8l4fGDX 8ZiGstGFHG+Hfpc4CqN5RSc0s0an5OrahZo2z2Pw5kh1r9N4MheIISG0TCZBguOlvI 0vti60ezltCh8d1luu5vdlLcGZ1bvBUku0hMS+ojmAXHyySxLPLiHjvQ9Z5UzQXA5T AmitiXTmK1shk3jAX7FRh/vrbPycLhjIbXKaqC5fcw/Cf+Mb3jBXKmD3+OWfSauozt ruvt1HOZ3Al4Wv6cAdFgojSHxxbijeUR96LlDJto9WtZBcow7fg0jJEDAE99Cbshvo 6nM6d6u+GvyDw== From: "Jiri Slaby (SUSE)" To: gregkh@linuxfoundation.org Cc: linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, "Jiri Slaby (SUSE)" Subject: [PATCH v2 05/31] tty: n_tty: use uint for space returned by tty_write_room() Date: Mon, 17 Mar 2025 08:00:20 +0100 Message-ID: <20250317070046.24386-6-jirislaby@kernel.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250317070046.24386-1-jirislaby@kernel.org> References: <20250317070046.24386-1-jirislaby@kernel.org> Precedence: bulk X-Mailing-List: linux-serial@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 tty_write_room() returns an "unsigned int". So in case some insane driver (like my tty test driver) returns (legitimate) UINT_MAX from its tty_operations::write_room(), n_tty is confused on several places. For example, in process_output_block(), the result of tty_write_room() is stored into (signed) "int". So this UINT_MAX suddenly becomes -1. And that is extended to ssize_t and returned from process_output_block(). This causes a write() to such a node to receive -EPERM (which is -1). Fix that by using proper "unsigned int" and proper "== 0" test. And return 0 constant directly in that "if", so that it is immediately clear what is returned ("space" equals to 0 at that point). Similarly for process_output() and __process_echoes(). Note this does not fix any in-tree driver as of now. If you want "Fixes: something", it would be commit 03b3b1a2405c ("tty: make tty_operations::write_room return uint"). I intentionally do not mark this patch by a real tag below. Signed-off-by: Jiri Slaby (SUSE) --- drivers/tty/n_tty.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c index 2c5995019dd1..765d24268d75 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -488,7 +488,8 @@ static int do_output_char(u8 c, struct tty_struct *tty, int space) static int process_output(u8 c, struct tty_struct *tty) { struct n_tty_data *ldata = tty->disc_data; - int space, retval; + unsigned int space; + int retval; mutex_lock(&ldata->output_lock); @@ -524,16 +525,16 @@ static ssize_t process_output_block(struct tty_struct *tty, const u8 *buf, unsigned int nr) { struct n_tty_data *ldata = tty->disc_data; - int space; - int i; + unsigned int space; + int i; const u8 *cp; mutex_lock(&ldata->output_lock); space = tty_write_room(tty); - if (space <= 0) { + if (space == 0) { mutex_unlock(&ldata->output_lock); - return space; + return 0; } if (nr > space) nr = space; @@ -698,7 +699,7 @@ static int n_tty_process_echo_ops(struct tty_struct *tty, size_t *tail, static size_t __process_echoes(struct tty_struct *tty) { struct n_tty_data *ldata = tty->disc_data; - int space, old_space; + unsigned int space, old_space; size_t tail; u8 c;