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 2134A45C6E6; Thu, 30 Jul 2026 16:19:37 +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=1785428379; cv=none; b=ZIQcDHo2bMXokd1lfaaCaZjwlwBdNKIY6AwwjjXtgQPNEK93a88Y7BJVcn78todS0hOFYuJ3rfikbAmlSA9FkELBgrsXqPItOBpsDtxm9jQhFNuUfxjecT2q+rWbidABeKNQ+BKKl8xCynpbpH5z0OPScMzR+Uzp6GYpYLudAKs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785428379; c=relaxed/simple; bh=0E5556cEF/86q9Nxt49YB9AoDYsqlnwRU7N3yXmGaXQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Td+b4/fFDZGY6U0F4IAtXdeBExTgwMo3RL+O6lPzRuSzdBJxp06gtitzQZZAXe6kXwx6vgAfB++gQ/hEBobyXuDe9giurMdwjgVkLv9FokzQaEY2fEgtL8mqPoBfMywj7b1Nj9Mo4VDnh6/hsCXMq2fwAlC+vjm3YW2M6VWxC6U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=xjb5XdHB; 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="xjb5XdHB" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3CC9B1F000E9; Thu, 30 Jul 2026 16:19:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1785428377; bh=LBSRmBZqvSMofNWLtUeCzHkwk0Rv6M/cR5ZCysz+mVc=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=xjb5XdHB3bEwG5hD2Vgy9wHHpxY1Nx6jOh8fjWDWFq3wWJEZZjksW5khODV5MjOEa FTPmFjXrPLOXlVZLf48kCxK3POQBEbLgiH7H47ff4O55nKAwrtP6nwkRc+0xS3UMr+ VLHA0eFpHXqraRbrgydIh6Lw3YUjbY3RPUxe77yI= Date: Thu, 30 Jul 2026 16:31:51 +0200 From: Greg Kroah-Hartman To: Karl Mehltretter Cc: Jiri Slaby , Frank Li , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, imx@lists.linux.dev, linux-arm-kernel@lists.infradead.org, Sashiko , stable@vger.kernel.org Subject: Re: [PATCH v2 4/4] serial: imx: serialize imx_uart_ports[] lifetime Message-ID: <2026073011-crock-utmost-6392@gregkh> References: <20260719221014.44354-1-kmehltretter@gmail.com> <20260719221014.44354-5-kmehltretter@gmail.com> Precedence: bulk X-Mailing-List: linux-serial@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260719221014.44354-5-kmehltretter@gmail.com> On Mon, Jul 20, 2026 at 12:10:14AM +0200, Karl Mehltretter wrote: > imx_uart_probe() publishes the port in imx_uart_ports[] before > uart_add_one_port(), because console setup during that call uses the > table. The entry is not cleared if adding the port fails or after > imx_uart_remove() removes it. > > The port is devm-allocated, so a failed probe or unbind leaves the table > pointing at freed memory. A later registration of the shared console can > then dereference the stale entry. Reproduced on QEMU's mcimx6ul-evk by > unbinding a sibling UART, unbinding the console UART and rebinding the > sibling: > > BUG: KASAN: slab-use-after-free in imx_uart_console_setup+0xd0/0x3d8 > > The entry must remain valid until uart_remove_one_port() unregisters the > console. Clearing it afterward without serialization still races a > sibling probe: the sibling can register the shared console using the > dying entry before it is cleared. The next console write then > dereferences NULL. > > Use a driver-wide mutex to serialize table publication, port addition > and rollback with port removal and table clearing. Console callbacks > remain lockless because uart_add_one_port() may invoke setup while > probe holds the mutex. > > The probe-failure path also relies on "serial: core: do fallible > allocations before the console can be registered", which moves the > uport->name and uport->tty_groups allocations before console > registration. Both changes should be backported together. > > Fixes: dbff4e9ea2e8 ("IMX UART: remove statically initialized tables") > Fixes: 9f322ad064f9 ("imx: serial: handle initialisation failure correctly") > Reported-by: Sashiko > Link: https://lore.kernel.org/all/20260719162850.043B41F000E9@smtp.kernel.org > Cc: stable@vger.kernel.org > Assisted-by: Claude:claude-fable-5 > Signed-off-by: Karl Mehltretter > --- > drivers/tty/serial/imx.c | 21 +++++++++++++++++++-- > 1 file changed, 19 insertions(+), 2 deletions(-) > > diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c > index 251a50c8aa38..def874f9cd00 100644 > --- a/drivers/tty/serial/imx.c > +++ b/drivers/tty/serial/imx.c > @@ -22,6 +22,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -2080,6 +2081,15 @@ static const struct uart_ops imx_uart_pops = { > > static struct imx_port *imx_uart_ports[UART_NR]; > > +/* > + * Store the port in imx_uart_ports[] before uart_add_one_port() and clear > + * it only after uart_remove_one_port() returns. Console callbacks in both > + * calls use the table, so this mutex serializes these sequences between > + * sibling ports. Callbacks must not take it because uart_add_one_port() > + * may invoke setup while it is held. > + */ > +static DEFINE_MUTEX(imx_uart_ports_lock); Again, LLMs love to write comments/text, be sane please. This comment has nothing to do with the storing and such. > + > #if IS_ENABLED(CONFIG_SERIAL_IMX_CONSOLE) > static void imx_uart_console_putchar(struct uart_port *port, unsigned char ch) > { > @@ -2632,11 +2642,14 @@ static int imx_uart_probe(struct platform_device *pdev) > } > } > > - imx_uart_ports[sport->port.line] = sport; > - > platform_set_drvdata(pdev, sport); > > + mutex_lock(&imx_uart_ports_lock); guard()? > + imx_uart_ports[sport->port.line] = sport; > ret = uart_add_one_port(&imx_uart_uart_driver, &sport->port); > + if (ret) > + imx_uart_ports[sport->port.line] = NULL; > + mutex_unlock(&imx_uart_ports_lock); > > err_clk: > clk_disable_unprepare(sport->clk_ipg); > @@ -2647,8 +2660,12 @@ static int imx_uart_probe(struct platform_device *pdev) > static void imx_uart_remove(struct platform_device *pdev) > { > struct imx_port *sport = platform_get_drvdata(pdev); > + unsigned int line = sport->port.line; Why are you reading this outside of the lock? > > + mutex_lock(&imx_uart_ports_lock); guard()? thanks, greg k-h