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    SubjectRe: [Linux-fbdev-devel] fbcmap: non working tests on unsigned cmap->start
    Ville Syrjälä wrote:
    > On Sun, Apr 26, 2009 at 02:20:47PM +0200, Roel Kluin wrote:
    >> cmap->start is unsigned,

    >>> On Thu, Apr 23, 2009 at 01:41:10PM -0700, Andrew Morton wrote:
    >>>> argh.
    >>>>
    >>>> - Perhaps userspace can kill the kernel by sending a "negative"
    >>>> `start'. Removing the test will make it even less likely that we'll
    >>>> fix this bug.
    >>> Shouldn't happen. 'start' is used as the starting index for the hardware
    >>> palette, 'start+len-1' is the last index. All drivers should already check
    >>> the passed values since the maximum index depends on the display mode.
    >>> And I suppose the worst thing that could happen if the driver fails to
    >>> check the values would be incorrect colors.

    > You would rather need something like
    > 'if (start+len > 1 << max(red.len, green.len, blue.len, transp.len))'

    what do you mean with `red.len'? is that `info->var.red.length'?

    > and a check to make sure that start+len doesn't overflow.
    >
    > Oh and I guess it should also check that the visual is pseudocolor or
    > directcolor.

    I am fairly new so please review carefully.

    Not yet signed off-by: Roel Kluin <roel.kluin@gmail.com>
    ---
    diff --git a/drivers/video/fbcmap.c b/drivers/video/fbcmap.c
    index f53b9f1..b34e74e 100644
    --- a/drivers/video/fbcmap.c
    +++ b/drivers/video/fbcmap.c
    @@ -249,6 +249,7 @@ int fb_set_user_cmap(struct fb_cmap_user *cmap, struct fb_info *info)
    {
    int rc, size = cmap->len * sizeof(u16);
    struct fb_cmap umap;
    + __u32 rgba_max = 0;

    memset(&umap, 0, sizeof(struct fb_cmap));
    rc = fb_alloc_cmap(&umap, cmap->len, cmap->transp != NULL);
    @@ -261,13 +262,27 @@ int fb_set_user_cmap(struct fb_cmap_user *cmap, struct fb_info *info)
    rc = -EFAULT;
    goto out;
    }
    +
    + if (cmap->start + cmap->len < cmap->start) {
    + rc = -EINVAL;
    + goto out;
    + }
    +
    umap.start = cmap->start;
    if (!lock_fb_info(info)) {
    rc = -ENODEV;
    goto out;
    }
    - if (cmap->start < 0 || (!info->fbops->fb_setcolreg &&
    - !info->fbops->fb_setcmap)) {
    +
    + rgba_max = max(info->var.red.length, info->var.green.length);
    + rgba_max = max(rgba_max, info->var.blue.length);
    + rgba_max = max(rgba_max, info->var.transp.length);
    +
    + if (cmap->start + cmap->len > 1 << rgba_max ||
    + !(info->fbops->fb_setcolreg ||
    + info->fbops->fb_setcmap) ||
    + !(info->fix.visual == FB_VISUAL_PSEUDOCOLOR ||
    + info->fix.visual == FB_VISUAL_TRUECOLOR)) {
    rc = -EINVAL;
    goto out1;
    }
    --
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      Last update: 2009-04-27 14:01    [W:0.035 / U:36.040 seconds]
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