drm/i2c: tda998x: Remove VLA usage

There's an ongoing effort to remove VLAs[1] from the kernel to eventually
turn on -Wvla. The vla in reg_write_range is based on the length of data
passed. The one use of a non-constant size for this range is bounded by
the size buffer passed to hdmi_infoframe_pack which is a fixed size.
Switch to this upper bound.

[1] https://lkml.org/lkml/2018/3/7/621

Signed-off-by: Laura Abbott <labbott@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20180411010330.17866-1-labbott@redhat.com

diff --git a/drivers/gpu/drm/i2c/tda998x_drv.c b/drivers/gpu/drm/i2c/tda998x_drv.c
index 421c8a72369e3b77abd9a869badba552defd1056..0068d714d1bd6664135fb49b2b4eb7031168cca3 100644 (file)
--- a/drivers/gpu/drm/i2c/tda998x_drv.c
+++ b/drivers/gpu/drm/i2c/tda998x_drv.c
@@ -466,13 +466,22 @@ out:
        return ret;
 }
 
+#define MAX_WRITE_RANGE_BUF 32
+
 static void
 reg_write_range(struct tda998x_priv *priv, u16 reg, u8 *p, int cnt)
 {
        struct i2c_client *client = priv->hdmi;
-       u8 buf[cnt+1];
+       /* This is the maximum size of the buffer passed in */
+       u8 buf[MAX_WRITE_RANGE_BUF + 1];
        int ret;
 
+       if (cnt > MAX_WRITE_RANGE_BUF) {
+               dev_err(&client->dev, "Fixed write buffer too small (%d)\n",
+                               MAX_WRITE_RANGE_BUF);
+               return;
+       }
+
        buf[0] = REG2ADDR(reg);
        memcpy(&buf[1], p, cnt);
 
@@ -679,7 +688,7 @@ static void
 tda998x_write_if(struct tda998x_priv *priv, u8 bit, u16 addr,
                 union hdmi_infoframe *frame)
 {
-       u8 buf[32];
+       u8 buf[MAX_WRITE_RANGE_BUF];
        ssize_t len;
 
        len = hdmi_infoframe_pack(frame, buf, sizeof(buf));