[devel] Improved gamma range checks and other things OpenWatcom warns about.

1 files changed, 11 insertions, 10 deletions

diff --git a/pngset.c b/pngset.c
index 2c58f7fc7..5fe984120 100644
--- a/pngset.c
+++ b/pngset.c
@@ -94,15 +94,16 @@ png_set_gAMA_fixed(png_structp png_ptr, png_infop info_ptr, png_fixed_point
    if (png_ptr == NULL || info_ptr == NULL)
       return;
 
-   /* Previously these values were limited, however they must be
-    * wrong, therefore storing them (and setting PNG_INFO_gAMA)
-    * must be wrong too.
+   /* Changed in libpng-1.5.4 to limit the values to ensure overflow can't
+    * occur.  Since the fixed point representation is assymetrical it is
+    * possible for 1/gamma to overflow the limit of 21474 and this means the
+    * gamma value must be at least 5/100000 and hence at most 20000.0.  For
+    * safety the limits here are a little narrower.  The values are 0.00016 to
+    * 6250.0, which are truely ridiculous gammma values (and will produce
+    * displays that are all black or all white.)
     */
-   if (file_gamma > (png_fixed_point)PNG_UINT_31_MAX)
-      png_warning(png_ptr, "Gamma too large, ignored");
-
-   else if (file_gamma <= 0)
-      png_warning(png_ptr, "Negative or zero gamma ignored");
+   if (file_gamma < 16 || file_gamma > 625000000)
+      png_warning(png_ptr, "Out of range gamma value ignored");
 
    else
    {
@@ -340,11 +341,11 @@ png_set_sCAL_s(png_structp png_ptr, png_infop info_ptr,
    if (unit != 1 && unit != 2)
       png_error(png_ptr, "Invalid sCAL unit");
 
-   if (swidth == NULL || (lengthw = png_strlen(swidth)) <= 0 ||
+   if (swidth == NULL || (lengthw = png_strlen(swidth)) == 0 ||
        swidth[0] == 45 /* '-' */ || !png_check_fp_string(swidth, lengthw))
       png_error(png_ptr, "Invalid sCAL width");
 
-   if (sheight == NULL || (lengthh = png_strlen(sheight)) <= 0 ||
+   if (sheight == NULL || (lengthh = png_strlen(sheight)) == 0 ||
        sheight[0] == 45 /* '-' */ || !png_check_fp_string(sheight, lengthh))
       png_error(png_ptr, "Invalid sCAL height");