Re: [PATCH] unshare.2: note EINVAL when unsharing pid ns twice

"Michael Kerrisk (man-opages)" <mtk.manpages@xxxxxxxxx> · Fri, 28 Sep 2018 23:57:16 +0200

Hi Tycho!

On 09/28/2018 09:12 PM, Tycho Andersen wrote:
The kernel doesn't allow unsharing a pid NS if it has previously been
unshared, per this check in copy_pid_ns:

         if (task_active_pid_ns(current) != old_ns)
                 return ERR_PTR(-EINVAL);

so let's note that.

Thanks -- succinct commit message that captured the info that I
need to verify. (I also verified with a small test program.)

Patch applied.

Cheers,

Michael

Signed-off-by: Tycho Andersen <tycho@xxxxxxxx>
---
  man2/unshare.2 | 8 ++++++++
  1 file changed, 8 insertions(+)

diff --git a/man2/unshare.2 b/man2/unshare.2
index 5206eba6b..a24a627d8 100644
--- a/man2/unshare.2
+++ b/man2/unshare.2
@@ -330,6 +330,14 @@ but the kernel was not configured with the
  .B CONFIG_UTS_NS
  option.
  .TP
+.B EINVAL
+.BR CLONE_NEWPID
+was specified in
+.IR flags
+but there was a previous
+.BR unshare(CLONE_NEWPID)
+call.
+.TP
  .B ENOMEM
  Cannot allocate sufficient memory to copy parts of caller's
  context that need to be unshared.







