From: Douglas Anderson Date: Thu, 14 Dec 2023 20:37:52 +0000 (-0800) Subject: drm/bridge: ti-sn65dsi86: Never store more than msg->size bytes in AUX xfer X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=aca58eac52b88138ab98c814afb389a381725cd7;p=linux.git drm/bridge: ti-sn65dsi86: Never store more than msg->size bytes in AUX xfer For aux reads, the value `msg->size` indicates the size of the buffer provided by `msg->buffer`. We should never in any circumstances write more bytes to the buffer since it may overflow the buffer. In the ti-sn65dsi86 driver there is one code path that reads the transfer length from hardware. Even though it's never been seen to be a problem, we should make extra sure that the hardware isn't increasing the length since doing so would cause us to overrun the buffer. Fixes: 982f589bde7a ("drm/bridge: ti-sn65dsi86: Update reply on aux failures") Reviewed-by: Stephen Boyd Reviewed-by: Guenter Roeck Signed-off-by: Douglas Anderson Link: https://patchwork.freedesktop.org/patch/msgid/20231214123752.v3.2.I7b83c0f31aeedc6b1dc98c7c741d3e1f94f040f8@changeid --- diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c index c45c07840f645..b5464199b6334 100644 --- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c +++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c @@ -527,6 +527,7 @@ static ssize_t ti_sn_aux_transfer(struct drm_dp_aux *aux, u32 request_val = AUX_CMD_REQ(msg->request); u8 *buf = msg->buffer; unsigned int len = msg->size; + unsigned int short_len; unsigned int val; int ret; u8 addr_len[SN_AUX_LENGTH_REG + 1 - SN_AUX_ADDR_19_16_REG]; @@ -600,7 +601,8 @@ static ssize_t ti_sn_aux_transfer(struct drm_dp_aux *aux, } if (val & AUX_IRQ_STATUS_AUX_SHORT) { - ret = regmap_read(pdata->regmap, SN_AUX_LENGTH_REG, &len); + ret = regmap_read(pdata->regmap, SN_AUX_LENGTH_REG, &short_len); + len = min(len, short_len); if (ret) goto exit; } else if (val & AUX_IRQ_STATUS_NAT_I2C_FAIL) {