fix(gif): address corrupt files with bad resolutions and overflow int (#5257)

Signed-off-by: Larry Gritz <lg@larrygritz.com>

src/gif.imageio/gifinput.cpp

@@ -337,7 +337,8 @@ GIFInput::read_subimage_data()
 
     if (m_subimage == 0 || m_previous_disposal_method == DISPOSE_BACKGROUND) {
         // make whole canvas transparent
-        std::fill(m_canvas.begin(), m_canvas.end(), 0x00);
+        m_canvas.clear();
+        m_canvas.resize(m_spec.image_pixels() * size_t(4), 0x00);
     }
 
     // decode scanline index if image is interlaced
@@ -412,7 +413,6 @@ GIFInput::seek_subimage(int subimage, int miplevel)
             return false;
         }
         m_subimage = -1;
-        m_canvas.resize(m_gif_file->SWidth * m_gif_file->SHeight * 4);
     }
 
     // skip subimages preceding the requested one
@@ -436,6 +436,10 @@ GIFInput::seek_subimage(int subimage, int miplevel)
     m_spec.full_width  = m_spec.width;
     m_spec.full_depth  = m_spec.depth;
 
+    if (!check_open(m_spec, { 0, 32768, 0, 32768, 0, 1, 0, 4 })) {
+        return false;
+    }
+
     m_subimage = subimage;
 
     // draw subimage on canvas

testsuite/gif/ref/out.txt

@@ -106,3 +106,6 @@ tahoe-tiny.gif       :  128 x   96, 4 channel, uint8 gif
     oiio:ColorSpace: "srgb_rec709_scene"
     oiio:LoopCount: 0
     oiio:Movie: 1
+oiiotool ERROR: read : "src/crash_4163.gif": Wrong record type detected
+Full command line was:
+> oiiotool -nostderr -oiioattrib try_all_readers 0 src/crash_4163.gif -o test.exr

testsuite/gif/run.py

@@ -15,3 +15,8 @@ for f in files:
 # Test write / conversion to GIF
 command += oiiotool (OIIO_TESTSUITE_ROOT+"/common/tahoe-tiny.tif -o tahoe-tiny.gif")
 command += info_command ("tahoe-tiny.gif")
+
+# Regression tests
+command += oiiotool ("-nostderr -oiioattrib try_all_readers 0 src/crash_4163.gif -o test.exr", failureok = True)
+
+outputs = [ "tahoe-tiny.gif", "out.txt" ]