Move the deep check back into the loop. There are ways that even though

we're deep the code will SSTOP and sleep and then on wakeup we need to
recheck the deep conditions.
Issue analyzed and OK by mpi@

Reported-by: syzbot+f7634539e73108238c2a@syzkaller.appspotmail.com

diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
index 9516b02..e6eee8f 100644 (file)
--- a/sys/kern/kern_sig.c
+++ b/sys/kern/kern_sig.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: kern_sig.c,v 1.297 2022/06/28 12:08:17 claudio Exp $  */
+/*     $OpenBSD: kern_sig.c,v 1.298 2022/06/29 10:48:22 claudio Exp $  */
 /*     $NetBSD: kern_sig.c,v 1.54 1996/04/22 01:38:32 christos Exp $   */
 
 /*
@@ -2020,15 +2020,15 @@ single_thread_check_locked(struct proc *p, int deep, int s)
        SCHED_ASSERT_LOCKED();
 
        if (pr->ps_single != NULL && pr->ps_single != p) {
-               /* if we're in deep, we need to unwind to the edge */
-               if (deep) {
-                       if (pr->ps_flags & PS_SINGLEUNWIND)
-                               return (ERESTART);
-                       if (pr->ps_flags & PS_SINGLEEXIT)
-                               return (EINTR);
-               }
-
                do {
+                       /* if we're in deep, we need to unwind to the edge */
+                       if (deep) {
+                               if (pr->ps_flags & PS_SINGLEUNWIND)
+                                       return (ERESTART);
+                               if (pr->ps_flags & PS_SINGLEEXIT)
+                                       return (EINTR);
+                       }
+
                        if (atomic_dec_int_nv(&pr->ps_singlecount) == 0)
                                wakeup(&pr->ps_singlecount);