$ go version
go version devel +add507d4646f Tue Oct 08 13:13:40 2013 -0700 linux/amd64

What steps will reproduce the problem?
If possible, include a link to a program on play.golang.org.
1. Download will_hang.gz data file
2. Either download go_gunzip.go or take the program from
http://play.golang.org/p/cvnOQmWTRc

3. Run it
go go_gunzip.go < will_crash.gz

What is the expected output?
Before io.Copy
After io.Copy
<exit status 0>

What do you see instead?

$ go run go_gunzip.go < will_hang.gz                                                 
                            
2013/10/08 21:49:51 Before io.Copy

it hangs forever, eats 100% of CPU and never completes.

Which compiler are you using (5g, 6g, 8g, gccgo)?
6g

Which operating system are you using?
Ubuntu Linux 12.04 x86-64 (also tested on 13.04).

Which version are you using?  (run 'go version')

$ go version
go version devel +add507d4646f Tue Oct 08 13:13:40 2013 -0700 linux/amd64

Additional info:

I ran the program under gdb. Here is the example stack traces:

0x00000000004313c0 in compress/flate.(*decompressor).huffSym (f=0xc21006e000,
h=0xc21006e030, ~anon1=0, ~anon2=...)
    at /home/krasin/go/src/pkg/compress/flate/inflate.go:645
645                             chunk =
h.links[chunk>>huffmanValueShift][(f.b>>huffmanChunkBits)&h.linkMask]
(gdb) bt
#0  0x00000000004313c0 in compress/flate.(*decompressor).huffSym (f=0xc21006e000,
h=0xc21006e030, ~anon1=0, ~anon2=...)
    at /home/krasin/go/src/pkg/compress/flate/inflate.go:645
#1  0x000000000043038d in compress/flate.(*decompressor).huffmanBlock (f=0xc21006e000)
    at /home/krasin/go/src/pkg/compress/flate/inflate.go:395
#2  0x000000000042f8f4 in compress/flate.(*decompressor).Read (f=0xc21006e000, b=
[]uint8 = {...}, ~anon1=8192, ~anon2=...)
    at /home/krasin/go/src/pkg/compress/flate/inflate.go:275
#3  0x0000000000424b69 in compress/gzip.(*Reader).Read (z=0xc21005d000, p= []uint8 =
{...}, n=8192, err=...)
    at /home/krasin/go/src/pkg/compress/gzip/gunzip.go:207
#4  0x0000000000425f30 in io/ioutil.devNull.ReadFrom (r=..., n=102203392, err=...) at
/home/krasin/go/src/pkg/io/ioutil/ioutil.go:144
#5  0x0000000000425584 in io.Copy (dst=..., src=..., written=0, err=...) at
/home/krasin/go/src/pkg/io/io.go:348
#6  0x0000000000400ed8 in main.main () at /home/krasin/testdata/go_gunzip.go:22




0x000000000043228a in hash/crc32.update (crc=1794811569, tab=0xc210047000, p= []uint8 =
{...}, ~anon3=8192)
    at /home/krasin/go/src/pkg/hash/crc32/crc32.go:103
103             for _, v := range p {
(gdb) bt
#0  0x000000000043228a in hash/crc32.update (crc=1794811569, tab=0xc210047000, p=
[]uint8 = {...}, ~anon3=8192)
    at /home/krasin/go/src/pkg/hash/crc32/crc32.go:103
#1  0x000000000043234e in hash/crc32.Update (crc=1794811569, tab=0xc210047000, p=
[]uint8 = {...}, ~anon3=1794811569)
    at /home/krasin/go/src/pkg/hash/crc32/crc32.go:114
#2  0x00000000004323c6 in hash/crc32.(*digest).Write (d=0xc21000a230, p= []uint8 =
{...}, n=8192, err=...)
    at /home/krasin/go/src/pkg/hash/crc32/crc32.go:118
#3  0x0000000000424bd9 in compress/gzip.(*Reader).Read (z=0xc21005d000, p= []uint8 =
{...}, n=8192, err=...)
    at /home/krasin/go/src/pkg/compress/gzip/gunzip.go:208
#4  0x0000000000425f30 in io/ioutil.devNull.ReadFrom (r=..., n=184705024, err=...) at
/home/krasin/go/src/pkg/io/ioutil/ioutil.go:144
#5  0x0000000000425584 in io.Copy (dst=..., src=..., written=0, err=...) at
/home/krasin/go/src/pkg/io/io.go:348
#6  0x0000000000400ed8 in main.main () at /home/krasin/testdata/go_gunzip.go:22


P.S. There's also a false alarm from me here:
https://golang.org/issue/6549 Please, don't confuse this bug report
(which I believe to be real) and that one.

Attachments:

1. go_gunzip.go (396 bytes)
2. will_hang.gz (65536 bytes)