From b8f566b04d3cddd192cfd2418ae6d54ac6353792 Mon Sep 17 00:00:00 2001 From: Pavel Emelyanov Date: Thu, 12 Jan 2012 17:20:27 -0800 Subject: sysctl: add the kernel.ns_last_pid control The sysctl works on the current task's pid namespace, getting and setting its last_pid field. Writing is allowed for CAP_SYS_ADMIN-capable tasks thus making it possible to create a task with desired pid value. This ability is required badly for the checkpoint/restore in userspace. This approach suits all the parties for now. Signed-off-by: Pavel Emelyanov Acked-by: Tejun Heo Cc: Oleg Nesterov Cc: Cyrill Gorcunov Cc: "Eric W. Biederman" Cc: Serge Hallyn Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/pid.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'kernel/pid.c') diff --git a/kernel/pid.c b/kernel/pid.c index fa5f72227e5f..ce8e00deaccb 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -137,7 +137,9 @@ static int pid_before(int base, int a, int b) } /* - * We might be racing with someone else trying to set pid_ns->last_pid. + * We might be racing with someone else trying to set pid_ns->last_pid + * at the pid allocation time (there's also a sysctl for this, but racing + * with this one is OK, see comment in kernel/pid_namespace.c about it). * We want the winner to have the "later" value, because if the * "earlier" value prevails, then a pid may get reused immediately. * -- cgit v1.2.1