Add a resource limit for the total number of kqueues available to the

user.  Kqueue now saves the ucred of the allocating thread, to
correctly decrement the counter on close.

Under some specific and not real-world use scenario for kqueue, it is
possible for the kqueues to consume memory proportional to the square
of the number of the filedescriptors available to the process.  Limit
allows administrator to prevent the abuse.

This is kernel-mode side of the change, with the user-mode enabling
commit following.

Reported and tested by:	pho
Discussed with:	jmg
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks

3 files changed, 4 insertions, 0 deletions

diff --git a/lib/libc/sys/getrlimit.2 b/lib/libc/sys/getrlimit.2
index 35198bc..1f84bfb 100644
--- a/lib/libc/sys/getrlimit.2
+++ b/lib/libc/sys/getrlimit.2
@@ -108,6 +108,8 @@ Please see
 for a complete description of this sysctl.
 .It Dv RLIMIT_NPTS
 The maximum number of pseudo-terminals created by this user id.
+.It Dv RLIMIT_KQUEUES
+The maximum number of kqueues created by this user id.
 .El
 .Pp
 A resource limit is specified as a soft limit and a hard limit.
diff --git a/lib/libutil/login_class.3 b/lib/libutil/login_class.3
index 62a65f2..75f3614 100644
--- a/lib/libutil/login_class.3
+++ b/lib/libutil/login_class.3
@@ -118,6 +118,7 @@ sbsize           RLIMIT_SBSIZE
 vmemoryuse       RLIMIT_VMEM
 pseudoterminals  RLIMIT_NPTS
 swapuse          RLIMIT_SWAP
+kqueues          RLIMIT_KQUEUES
 .Ed
 .It LOGIN_SETPRIORITY
 Set the scheduling priority for the current process based on the
diff --git a/lib/libutil/login_class.c b/lib/libutil/login_class.c
index 263044f..39cce12 100644
--- a/lib/libutil/login_class.c
+++ b/lib/libutil/login_class.c
@@ -66,6 +66,7 @@ static struct login_res {
     { "vmemoryuse",      login_getcapsize, RLIMIT_VMEM    },
     { "pseudoterminals", login_getcapnum,  RLIMIT_NPTS    },
     { "swapuse",         login_getcapsize, RLIMIT_SWAP    },
+    { "kqueues",         login_getcapsize, RLIMIT_KQUEUES },
     { NULL,              0,                0              }
 };