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Wed, 10 Jun 2026 20:39:19 -0700 (PDT) From: Rosen Penev To: linux-serial@vger.kernel.org Cc: Greg Kroah-Hartman , Jiri Slaby , Frank Li , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , linux-kernel@vger.kernel.org (open list:TTY LAYER AND SERIAL DRIVERS), imx@lists.linux.dev (open list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE), linux-arm-kernel@lists.infradead.org (moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE) Subject: [PATCHv3 5/6] serial: mxs-auart: clamp RX DMA count to buffer size Date: Wed, 10 Jun 2026 20:38:55 -0700 Message-ID: <20260611033856.6476-6-rosenp@gmail.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260611033856.6476-1-rosenp@gmail.com> References: <20260611033856.6476-1-rosenp@gmail.com> Precedence: bulk X-Mailing-List: imx@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit In dma_rx_callback(), the RX count from the hardware status register (AUART_STAT_RXCOUNT_MASK = 0xffff) is passed directly to tty_insert_flip_string() without any bounds check. Since rx_dma_buf is allocated with UART_XMIT_SIZE (4096 bytes), a hardware fault or compromised peripheral reporting a count larger than 4096 would cause an out-of-bounds read, potentially leaking kernel memory. Clamp the count to UART_XMIT_SIZE before use. Assisted-by: opencode:big-pickle Signed-off-by: Rosen Penev --- drivers/tty/serial/mxs-auart.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/tty/serial/mxs-auart.c b/drivers/tty/serial/mxs-auart.c index e2b656638ab3..fe48a372d022 100644 --- a/drivers/tty/serial/mxs-auart.c +++ b/drivers/tty/serial/mxs-auart.c @@ -823,7 +823,7 @@ static void dma_rx_callback(void *arg) stat &= ~(AUART_STAT_OERR | AUART_STAT_BERR | AUART_STAT_PERR | AUART_STAT_FERR); - count = stat & AUART_STAT_RXCOUNT_MASK; + count = min_t(u32, stat & AUART_STAT_RXCOUNT_MASK, UART_XMIT_SIZE); tty_insert_flip_string(port, s->rx_dma_buf, count); mxs_write(stat, s, REG_STAT); -- 2.54.0