5.15-stable review patch. If anyone has any objections, please let me know.
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From: Douglas Anderson dianders@chromium.org
[ Upstream commit aca58eac52b88138ab98c814afb389a381725cd7 ]
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 swboyd@chromium.org Reviewed-by: Guenter Roeck groeck@chromium.org Signed-off-by: Douglas Anderson dianders@chromium.org Link: https://patchwork.freedesktop.org/patch/msgid/20231214123752.v3.2.I7b83c0f31... Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpu/drm/bridge/ti-sn65dsi86.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c index 22c2ff5272c60..b488c6cb8f106 100644 --- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c +++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c @@ -471,6 +471,7 @@ 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]; @@ -544,7 +545,8 @@ 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) {