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syscall: use fcntl with F_DUP2FD_CLOEXEC in forkAndExecInChild on Fre…
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…eBSD

Use fcntl(oldfd, F_DUP2FD_CLOEXEC, newfd) to duplicate the file
descriptor and mark is as close-on-exec instead of dup2 & fcntl.

FreeBSD implements dup3 like this in libc.

Change-Id: I36e37bc61c2e31561adb49001f287764125a74de
Reviewed-on: https://go-review.googlesource.com/c/go/+/355571
Trust: Tobias Klauser <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
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tklauser committed Oct 14, 2021
1 parent 2feb2cc commit 24e798e
Showing 1 changed file with 2 additions and 4 deletions.
6 changes: 2 additions & 4 deletions src/syscall/exec_freebsd.go
Original file line number Diff line number Diff line change
Expand Up @@ -214,11 +214,10 @@ func forkAndExecInChild(argv0 *byte, argv, envv []*byte, chroot, dir *byte, attr
// Pass 1: look for fd[i] < i and move those up above len(fd)
// so that pass 2 won't stomp on an fd it needs later.
if pipe < nextfd {
_, _, err1 = RawSyscall(SYS_DUP2, uintptr(pipe), uintptr(nextfd), 0)
_, _, err1 = RawSyscall(SYS_FCNTL, uintptr(pipe), F_DUP2FD_CLOEXEC, uintptr(nextfd))
if err1 != 0 {
goto childerror
}
RawSyscall(SYS_FCNTL, uintptr(nextfd), F_SETFD, FD_CLOEXEC)
pipe = nextfd
nextfd++
}
Expand All @@ -227,11 +226,10 @@ func forkAndExecInChild(argv0 *byte, argv, envv []*byte, chroot, dir *byte, attr
if nextfd == pipe { // don't stomp on pipe
nextfd++
}
_, _, err1 = RawSyscall(SYS_DUP2, uintptr(fd[i]), uintptr(nextfd), 0)
_, _, err1 = RawSyscall(SYS_FCNTL, uintptr(fd[i]), F_DUP2FD_CLOEXEC, uintptr(nextfd))
if err1 != 0 {
goto childerror
}
RawSyscall(SYS_FCNTL, uintptr(nextfd), F_SETFD, FD_CLOEXEC)
fd[i] = nextfd
nextfd++
}
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