From 9a9254c4a2a3ca2b3da16d173f3b0dd01f397ff6 Mon Sep 17 00:00:00 2001 From: Shitalkumar Gandhi Date: Mon, 20 Apr 2026 19:29:03 +0530 Subject: [PATCH] serial: fsl_lpuart: fix rx buffer and DMA map leaks in start_rx_dma lpuart_start_rx_dma() allocates sport->rx_ring.buf with kzalloc() and then maps a scatterlist via dma_map_sg(). On three subsequent error paths the function returns directly without releasing those resources: - when dma_map_sg() returns 0 (-EINVAL): ring->buf is leaked. - when dmaengine_slave_config() fails: ring->buf and the DMA mapping are leaked. - when dmaengine_prep_dma_cyclic() returns NULL: ring->buf and the DMA mapping are leaked. The sole cleanup path, lpuart_dma_rx_free(), is only reached when lpuart_dma_rx_use is set, and the caller lpuart_rx_dma_startup() clears that flag on failure of lpuart_start_rx_dma(). So these resources are permanently leaked on every failure in this function. Repeated port open/close or termios changes under error conditions will slowly consume memory and leave stale streaming DMA mappings behind. Fix it by introducing two error labels that unmap the scatterlist and free the ring buffer as appropriate. While here, replace the misleading -EFAULT (bad userspace pointer) returned when dmaengine_prep_dma_cyclic() fails with the more accurate -ENOMEM, matching how other dmaengine users in the tree treat this failure. No functional change on the success path. Fixes: 5887ad43ee02 ("tty: serial: fsl_lpuart: Use cyclic DMA for Rx") Cc: stable Signed-off-by: Shitalkumar Gandhi Reviewed-by: Frank Li Link: https://patch.msgid.link/20260420135903.2062024-1-shitalkumar.gandhi@cambiumnetworks.com Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/fsl_lpuart.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c index 1bd7ec9c81ea..b7919c05f0fb 100644 --- a/drivers/tty/serial/fsl_lpuart.c +++ b/drivers/tty/serial/fsl_lpuart.c @@ -1379,7 +1379,8 @@ static inline int lpuart_start_rx_dma(struct lpuart_port *sport) if (!nent) { dev_err(sport->port.dev, "DMA Rx mapping error\n"); - return -EINVAL; + ret = -EINVAL; + goto err_free_buf; } dma_rx_sconfig.src_addr = lpuart_dma_datareg_addr(sport); @@ -1391,7 +1392,7 @@ static inline int lpuart_start_rx_dma(struct lpuart_port *sport) if (ret < 0) { dev_err(sport->port.dev, "DMA Rx slave config failed, err = %d\n", ret); - return ret; + goto err_unmap_sg; } sport->dma_rx_desc = dmaengine_prep_dma_cyclic(chan, @@ -1402,7 +1403,8 @@ static inline int lpuart_start_rx_dma(struct lpuart_port *sport) DMA_PREP_INTERRUPT); if (!sport->dma_rx_desc) { dev_err(sport->port.dev, "Cannot prepare cyclic DMA\n"); - return -EFAULT; + ret = -ENOMEM; + goto err_unmap_sg; } sport->dma_rx_desc->callback = lpuart_dma_rx_complete; @@ -1426,6 +1428,13 @@ static inline int lpuart_start_rx_dma(struct lpuart_port *sport) } return 0; + +err_unmap_sg: + dma_unmap_sg(chan->device->dev, &sport->rx_sgl, 1, DMA_FROM_DEVICE); +err_free_buf: + kfree(ring->buf); + ring->buf = NULL; + return ret; } static void lpuart_dma_rx_free(struct uart_port *port)