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pid_namespaces.7: Mention unshare()+fork() failure case if "init" terminates 

Reported-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Michael Kerrisk 2013-03-01 11:19:14 +01:00
parent 5597d425e9
commit 81ccc85366
1 changed files with 15 additions and 6 deletions
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21
man7/pid_namespaces.7
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@ -79,15 +79,24 @@ This behavior reflects the fact that the "init" process
is essential for the correct operation of a PID namespace.
In this case, a subsequent
.BR fork (2)
into this PID namespace (e.g., from a process that has done a
.BR setns (2)
into the namespace using an open file descriptor for a
.I /proc/[pid]/ns/pid
file corresponding to a process that was in the namespace)
will fail with the error
into this PID namespace will fail with the error
.BR ENOMEM ;
it is not possible to create a new processes in a PID namespace whose "init"
process has terminated.
Such scenarios can occur when, for example,
a process uses an open file descriptor for a
.I /proc/[pid]/ns/pid
file corresponding to a process that was in a namespace to
.BR setns (2)
into that namespace after the "init" process has terminated.
Another possible scenario can occur after a call to
.BR unshare (2):
if the first child subsequently created by a
.BR fork (2)
terminates, then subsequent calls to
.BR fork (2)
will fail with
.BR ENOMEM .
Only signals for which the "init" process has established a signal handler
can be sent to the "init" process by other members of the PID namespace.