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syscall: fix accidental close of exec status pipe in StartProcess

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In syscall.forkAndExecInChild, blocks of code labelled Pass 1
and Pass 2 permute the file descriptors (if necessary) which are
passed to the child process.  If Pass 1 begins with fds = {0,2,1},
nextfd = 4 and pipe = 4, then the statement labelled "don't stomp
on pipe" is too late -- the pipe (which will be needed to pass
exec status back to the parent) will have been closed by the
preceding DUP call.

Moving the "don't stomp" test earlier ensures that the pipe is
protected.

Fixes #14979

Change-Id: I890c311527f6aa255be48b3277c1e84e2049ee22
Reviewed-on: https://go-review.googlesource.com/21184
Run-TryBot: David du Colombier <0intro@gmail.com>
Reviewed-by: David du Colombier <0intro@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
Richard Miller 2016-03-26 19:35:21 +00:00 • committed by Brad Fitzpatrick
parent 272df158ac
commit 1f0bebcc72
5 changed files with 26 additions and 12 deletions
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6
src/syscall/exec_linux.go
View file

@ -255,6 +255,9 @@ func forkAndExecInChild(argv0 *byte, argv, envv []*byte, chroot, dir *byte, attr
}
for i = 0; i < len(fd); i++ {
if fd[i] >= 0 && fd[i] < int(i) {
if nextfd == pipe { // don't stomp on pipe
nextfd++
}
_, _, err1 = RawSyscall(_SYS_dup, uintptr(fd[i]), uintptr(nextfd), 0)
if err1 != 0 {
goto childerror
@ -262,9 +265,6 @@ func forkAndExecInChild(argv0 *byte, argv, envv []*byte, chroot, dir *byte, attr
RawSyscall(SYS_FCNTL, uintptr(nextfd), F_SETFD, FD_CLOEXEC)
fd[i] = nextfd
nextfd++
if nextfd == pipe { // don't stomp on pipe
nextfd++
}
}
}