image/jpeg: when following component selectors, only consider valid

components.

This fixes decoding JPEG images where the component selector is 0. Such
images are rare, but not impossible.

Change-Id: I6d221bce01cce8cc0440e117543233371782ca22
Reviewed-on: https://go-review.googlesource.com/6421
Reviewed-by: Rob Pike <r@golang.org>

diff --git a/src/image/jpeg/scan.go b/src/image/jpeg/scan.go
index 8fcf401dd836ea6a0c9ba589b9ebbd8c8d4d431f..da60023fb52b5967c821d3a0c203bdbb38da4cf9 100644 (file)
--- a/src/image/jpeg/scan.go
+++ b/src/image/jpeg/scan.go
@@ -66,7 +66,7 @@ func (d *decoder) processSOS(n int) error {
        for i := 0; i < nComp; i++ {
                cs := d.tmp[1+2*i] // Component selector.
                compIndex := -1
-               for j, comp := range d.comp {
+               for j, comp := range d.comp[:d.nComp] {
                        if cs == comp.c {
                                compIndex = j
                        }