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fix a race crash when building with "ADD some-broken.tar.xz ..."

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The race is between pools.Put which calls buf.Reset and exec.Cmd
doing io.Copy from the buffer; it caused a runtime crash, as
described in #16924:

``` docker-daemon cat the-tarball.xz | xz -d -c -q | docker-untar /path/to/... (aufs ) ```

When docker-untar side fails (like try to set xattr on aufs, or a broken
tar), invokeUnpack will be responsible to exhaust all input, otherwise
`xz` will be write pending for ever.

this change add a receive only channel to cmdStream, and will close it
to notify it's now safe to close the input stream;

in CmdStream the change to use Stdin / Stdout / Stderr keeps the
code simple, os/exec.Cmd will spawn goroutines and call io.Copy automatically.

the CmdStream is actually called in the same file only, change it
lowercase to mark as private.

[...]
INFO[0000] Docker daemon                                 commit=0a8c2e3 execdriver=native-0.2 graphdriver=aufs version=1.8.2

DEBU[0006] Calling POST /build
INFO[0006] POST /v1.20/build?cgroupparent=&cpuperiod=0&cpuquota=0&cpusetcpus=&cpusetmems=&cpushares=0&dockerfile=Dockerfile&memory=0&memswap=0&rm=1&t=gentoo-x32&ulimits=null
DEBU[0008] [BUILDER] Cache miss
DEBU[0009] Couldn't untar /home/lib-docker-v1.8.2-tmp/tmp/docker-build316710953/stage3-x32-20151004.tar.xz to /home/lib-docker-v1.8.2-tmp/aufs/mnt/d909abb87150463939c13e8a349b889a72d9b14f0cfcab42a8711979be285537: Untar re-exec error: exit status 1: output: operation not supported
DEBU[0009] CopyFileWithTar(/home/lib-docker-v1.8.2-tmp/tmp/docker-build316710953/stage3-x32-20151004.tar.xz, /home/lib-docker-v1.8.2-tmp/aufs/mnt/d909abb87150463939c13e8a349b889a72d9b14f0cfcab42a8711979be285537/)
panic: runtime error: slice bounds out of range

goroutine 42 [running]:
bufio.(*Reader).fill(0xc208187800)
    /usr/local/go/src/bufio/bufio.go:86 +0x2db
bufio.(*Reader).WriteTo(0xc208187800, 0x7ff39602d150, 0xc2083f11a0, 0x508000, 0x0, 0x0)
    /usr/local/go/src/bufio/bufio.go:449 +0x27e
io.Copy(0x7ff39602d150, 0xc2083f11a0, 0x7ff3960261f8, 0xc208187800, 0x0, 0x0, 0x0)
    /usr/local/go/src/io/io.go:354 +0xb2
github.com/docker/docker/pkg/archive.func·006()
    /go/src/github.com/docker/docker/pkg/archive/archive.go:817 +0x71
created by github.com/docker/docker/pkg/archive.CmdStream
    /go/src/github.com/docker/docker/pkg/archive/archive.go:819 +0x1ec

goroutine 1 [chan receive]:
main.(*DaemonCli).CmdDaemon(0xc20809da30, 0xc20800a020, 0xd, 0xd, 0x0, 0x0)
    /go/src/github.com/docker/docker/docker/daemon.go:289 +0x1781
reflect.callMethod(0xc208140090, 0xc20828fce0)
    /usr/local/go/src/reflect/value.go:605 +0x179
reflect.methodValueCall(0xc20800a020, 0xd, 0xd, 0x1, 0xc208140090, 0x0, 0x0, 0xc208140090, 0x0, 0x45343f, ...)
    /usr/local/go/src/reflect/asm_amd64.s:29 +0x36
github.com/docker/docker/cli.(*Cli).Run(0xc208129fb0, 0xc20800a010, 0xe, 0xe, 0x0, 0x0)
    /go/src/github.com/docker/docker/cli/cli.go:89 +0x38e
main.main()
    /go/src/github.com/docker/docker/docker/docker.go:69 +0x428

goroutine 5 [syscall]:
os/signal.loop()
    /usr/local/go/src/os/signal/signal_unix.go:21 +0x1f
created by os/signal.init·1
    /usr/local/go/src/os/signal/signal_unix.go:27 +0x35

Signed-off-by: Derek Ch <denc716@gmail.com>
This commit is contained in:
Derek Ch 2015-10-10 03:24:21 +07:30 • committed by Derek
parent 831c2e7a7b
commit c45a95b9c0
3 changed files with 34 additions and 48 deletions
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6
chrootarchive/archive_unix.go
View file

@ -8,6 +8,7 @@ import (
"flag"
"fmt"
"io"
"io/ioutil"
"os"
"runtime"
"syscall"
@ -79,6 +80,11 @@ func invokeUnpack(decompressedArchive io.Reader, dest string, options *archive.T
w.Close()
if err := cmd.Wait(); err != nil {
// when `xz -d -c -q | docker-untar ...` failed on docker-untar side,
// we need to exhaust `xz`'s output, otherwise the `xz` side will be
// pending on write pipe forever
io.Copy(ioutil.Discard, decompressedArchive)
return fmt.Errorf("Untar re-exec error: %v: output: %s", err, output)
}
return nil