Re: [PATCH] fbdev: colormap fixes

Geert Uytterhoeven
2005-07-28T08:02:50Z

On Wed, 27 Jul 2005, Linux Kernel Mailing List wrote:
> tree 17014af0ea8b19dae7848736d324499715b7a1a3
> parent 3ca34fcbfbf8a7cbe99d54ae81c4e28fdc6f4ac6
> author Jon Smirl <jonsmirl@gmail.com> Thu, 28 Jul 2005 01:46:05 -0700
> committer Linus Torvalds <torvalds@g5.osdl.org> Thu, 28 Jul 2005 06:26:18 -0700
>
> [PATCH] fbdev: colormap fixes
>
> Color maps have up to 256 entries. 4096/256 allows for 16 characters per
^^^^^^^^^^^^^^^^^^^^^^
Most (all?) current drivers have this limitation. But there exists hardware
with more entries.

> line. The format for a cmap entry is "%02x%c%4x%4x%4x\n" %02x entry %c
> transp %4x red %4x blue %4x green
>
> You can read the color_map with cat fb0/color_map.
>
> Signed-off-by: Jon Smirl <jonsmirl@gmail.com>
> Signed-off-by: Andrew Morton <akpm@osdl.org>
> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
>
> drivers/video/fbsysfs.c | 82 ++++++++++++++++++++++++++++++++++++++++++------
> 1 files changed, 72 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/video/fbsysfs.c b/drivers/video/fbsysfs.c
> --- a/drivers/video/fbsysfs.c
> +++ b/drivers/video/fbsysfs.c
> @@ -242,10 +242,68 @@ static ssize_t show_virtual(struct class
> fb_info->var.yres_virtual);
> }
>
> -static ssize_t store_cmap(struct class_device *class_device, const char * buf,
> +/* Format for cmap is "%02x%c%4x%4x%4x\n" */
> +/* %02x entry %c transp %4x red %4x blue %4x green \n */
> +/* 255 rows at 16 chars equals 4096 */
^^^
256?

> +/* PAGE_SIZE can be 4096 or larger */
> +static ssize_t store_cmap(struct class_device *class_device, const char *buf,
> size_t count)
> {
> -// struct fb_info *fb_info = (struct fb_info *)class_get_devdata(class_device);
> + struct fb_info *fb_info = (struct fb_info *)class_get_devdata(class_device);
> + int rc, i, start, length, transp = 0;
> +
> + if ((count > 4096) || ((count % 16) != 0) || (PAGE_SIZE < 4096))
> + return -EINVAL;
> +
> + if (!fb_info->fbops->fb_setcolreg && !fb_info->fbops->fb_setcmap)
> + return -EINVAL;
> +
> + sscanf(buf, "%02x", &start);
> + length = count / 16;
> +
> + for (i = 0; i < length; i++)
> + if (buf[i * 16 + 2] != ' ')
> + transp = 1;
> +
> + /* If we can batch, do it */
> + if (fb_info->fbops->fb_setcmap && length > 1) {
> + struct fb_cmap umap;
> +
> + memset(&umap, 0, sizeof(umap));
> + if ((rc = fb_alloc_cmap(&umap, length, transp)))
> + return rc;
> +
> + umap.start = start;
> + for (i = 0; i < length; i++) {
> + sscanf(&buf[i * 16 + 3], "%4hx", &umap.red[i]);
> + sscanf(&buf[i * 16 + 7], "%4hx", &umap.blue[i]);
> + sscanf(&buf[i * 16 + 11], "%4hx", &umap.green[i]);
> + if (transp)
> + umap.transp[i] = (buf[i * 16 + 2] != ' ');
> + }
> + rc = fb_info->fbops->fb_setcmap(&umap, fb_info);
> + fb_copy_cmap(&umap, &fb_info->cmap);
> + fb_dealloc_cmap(&umap);
> +
> + return rc;
> + }
> + for (i = 0; i < length; i++) {
> + u16 red, blue, green, tsp;
> +
> + sscanf(&buf[i * 16 + 3], "%4hx", &red);
> + sscanf(&buf[i * 16 + 7], "%4hx", &blue);
> + sscanf(&buf[i * 16 + 11], "%4hx", &green);
> + tsp = (buf[i * 16 + 2] != ' ');
> + if ((rc = fb_info->fbops->fb_setcolreg(start++,
> + red, green, blue, tsp, fb_info)))
> + return rc;
> +
> + fb_info->cmap.red[i] = red;
> + fb_info->cmap.blue[i] = blue;
> + fb_info->cmap.green[i] = green;
> + if (transp)
> + fb_info->cmap.transp[i] = tsp;
> + }
> return 0;
> }
>
> @@ -253,20 +311,24 @@ static ssize_t show_cmap(struct class_de
> {
> struct fb_info *fb_info =
> (struct fb_info *)class_get_devdata(class_device);
> - unsigned int offset = 0, i;
> + unsigned int i;
>
> if (!fb_info->cmap.red || !fb_info->cmap.blue ||
> - !fb_info->cmap.green || !fb_info->cmap.transp)
> + !fb_info->cmap.green)
> + return -EINVAL;
> +
> + if (PAGE_SIZE < 4096)
> return -EINVAL;
>
> + /* don't mess with the format, the buffer is PAGE_SIZE */
> + /* 255 entries at 16 chars per line equals 4096 = PAGE_SIZE */
^^^
256?

> for (i = 0; i < fb_info->cmap.len; i++) {
> - offset += snprintf(buf, PAGE_SIZE - offset,
> - "%d,%d,%d,%d,%d\n", i + fb_info->cmap.start,
> - fb_info->cmap.red[i], fb_info->cmap.blue[i],
> - fb_info->cmap.green[i],
> - fb_info->cmap.transp[i]);
> + sprintf(&buf[ i * 16], "%02x%c%4x%4x%4x\n", i + fb_info->cmap.start,

Woops, nice buffer overflow if fb_info->cmap.len > 256...

> + ((fb_info->cmap.transp && fb_info->cmap.transp[i]) ? '*' : ' '),
> + fb_info->cmap.red[i], fb_info->cmap.blue[i],
> + fb_info->cmap.green[i]);
> }
> - return offset;
> + return 4096;
^^^^

What if fb_info->cmap.len is smaller than 256?

> }

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds