svn commit: r351174 - head/sys/kern

[Mateusz Guzik]

Author: mjg
Date: Sat Aug 17 17:56:43 2019
New Revision: 351174
URL: https://svnweb.freebsd.org/changeset/base/351174

Log:
  fork: bump process count before checking for permission to cross the limit
  
  The limit is almost never reached. Do the check only on failure to see if
  we can override it.
  
  No change in user-visible behavior.
  
  Sponsored by:	The FreeBSD Foundation

Modified:
  head/sys/kern/kern_fork.c

Modified: head/sys/kern/kern_fork.c
==============================================================================
--- head/sys/kern/kern_fork.c	Sat Aug 17 17:42:01 2019	(r351173)
+++ head/sys/kern/kern_fork.c	Sat Aug 17 17:56:43 2019	(r351174)
@@ -800,9 +800,10 @@ fork1(struct thread *td, struct fork_req *fr)
 	struct proc *p1, *newproc;
 	struct thread *td2;
 	struct vmspace *vm2;
+	struct ucred *cred;
 	struct file *fp_procdesc;
 	vm_ooffset_t mem_charged;
-	int error, nprocs_new, ok;
+	int error, nprocs_new;
 	static int curfail;
 	static struct timeval lastfail;
 	int flags, pages;
@@ -973,21 +974,17 @@ fork1(struct thread *td, struct fork_req *fr)
 	/*
 	 * Increment the count of procs running with this uid. Don't allow
 	 * a nonprivileged user to exceed their current limit.
-	 *
-	 * XXXRW: Can we avoid privilege here if it's not needed?
 	 */
-	error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT);
-	if (error == 0)
-		ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0);
-	else {
-		ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1,
-		    lim_cur(td, RLIMIT_NPROC));
+	cred = td->td_ucred;
+	if (!chgproccnt(cred->cr_ruidinfo, 1, lim_cur(td, RLIMIT_NPROC))) {
+		if (priv_check_cred(cred, PRIV_PROC_LIMIT) != 0)
+			goto fail0;
+		chgproccnt(cred->cr_ruidinfo, 1, 0);
 	}
-	if (ok) {
-		do_fork(td, fr, newproc, td2, vm2, fp_procdesc);
-		return (0);
-	}
 
+	do_fork(td, fr, newproc, td2, vm2, fp_procdesc);
+	return (0);
+fail0:
 	error = EAGAIN;
 	sx_xunlock(&allproc_lock);
 #ifdef MAC