image/gif: image block is out of bounds

[dvyukov]

The following program crashes with "image block is out of bounds". Either Decode should not produce such image, or Encode should accept it.

package main

import (
    "bytes"
    "image/gif"
    "strings"
)

func main() {
    img, err := gif.Decode(strings.NewReader(data))
    if err != nil {
        return
    }
    var w bytes.Buffer
    err = gif.Encode(&w, img, nil)
    if err != nil {
        panic(err)
    }
}

var data = "GIF89a0000000,0\x000\x00\x1e\x00" +
    "\x14\x00\x8600000000000000000" +
    "00000000000000000000" +
    "00000000000000000000" +
    "00000000000000000000" +
    "00000000000000000000" +
    "00000000000000000000" +
    "00000000000000000000" +
    "00000000000000000000" +
    "00000U\xa1\xb1$\x9b\x9e\x97\xb97,\xaf\x1ay\xa4\x14" +
    "\xea3\x96\x97\xc6e_\x10G\x8eS\xd2Mm\xa9\xa0\x19\xefF\xfe" +
    "\x97ợ.\xd0;0\x97\x14\xd50v!\xfbȒ\xe2ߗ" +
    "_}\x99`\v״\x98\xa8\xe0\xbdݺ\xaa\xce6\xd2MT " +
    "p\xe03\xdb\x10?J\xa8\xbe\xdc\xd1\x13\x89f\x05\xc4n;\xf3\x1c" +
    "\b5\xe0\x91\xdf\xde\x12qE<\xd6P\xf1O\x88\x8aD\xdf\u007f\xbc" +
    "\xc9Ͱ\x99\xb7\xe7n\u008dN9l\xca\xd0k8\x8e\xee\x84\xcb" +
    "\xbd\xf6K\x03\xc2s\x80|\xfb\xe91r\xbc\xfb\xeeu\x12r\u007f\xc0" +
    "}ȩ\xad\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" +
    "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" +
    "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" +
    "\x00\x00\x00\x00\x00\x00\x00\a$F\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b" +
    "\x8c\x8d\x8e\x8f\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f" +
    "\xa0\xa1\xa2\x85\x81\x00;"

panic: gif: image block is out of bounds

goroutine 1 [running]:
main.main()
    gif.go:17 +0x19d

go version devel +fbb4c74 Sat May 2 02:48:32 2015 +0000 darwin/amd64

[gopherbot]

CL https://golang.org/cl/9712 mentions this issue.