svn commit: r360940 - head/sys/kern

[Konstantin Belousov]

Author: kib
Date: Mon May 11 22:38:32 2020
New Revision: 360940
URL: https://svnweb.freebsd.org/changeset/base/360940

Log:
  sigfastblock: fix delivery of the pending signals in single-threaded processes.
  
  If single-threaded process receives a signal during critical section
  established by sigfastblock(2) word, unblock did not caused signal
  delivery because sigfastblock(SIGFASTBLOCK_UNBLOCK) failed to request
  ast handling of the pending signals.
  
  Set TDF_ASTPENDING | TDF_NEEDSIGCHK on unblock or when kernel forces
  end of sigfastblock critical section, to cause syscall exit to recheck
  and deliver any signal pending.
  
  Reported by:	corydoras at ridiculousfish.com
  PR:	246385
  Sponsored by:	The FreeBSD Foundation

Modified:
  head/sys/kern/kern_sig.c

Modified: head/sys/kern/kern_sig.c
==============================================================================
--- head/sys/kern/kern_sig.c	Mon May 11 22:26:39 2020	(r360939)
+++ head/sys/kern/kern_sig.c	Mon May 11 22:38:32 2020	(r360940)
@@ -3976,6 +3976,22 @@ sigfastblock_fetch_sig(struct thread *td, bool sendsig
 	return (true);
 }
 
+static void
+sigfastblock_resched(struct thread *td, bool resched)
+{
+	struct proc *p;
+
+	if (resched) {
+		p = td->td_proc;
+		PROC_LOCK(p);
+		reschedule_signals(p, td->td_sigmask, 0);
+		PROC_UNLOCK(p);
+	}
+	thread_lock(td);
+	td->td_flags |= TDF_ASTPENDING | TDF_NEEDSIGCHK;
+	thread_unlock(td);
+}
+
 int
 sys_sigfastblock(struct thread *td, struct sigfastblock_args *uap)
 {
@@ -4046,11 +4062,8 @@ sys_sigfastblock(struct thread *td, struct sigfastbloc
 		 * signals to current thread.  But notify others about
 		 * fake unblock.
 		 */
-		if (error == 0 && p->p_numthreads != 1) {
-			PROC_LOCK(p);
-			reschedule_signals(p, td->td_sigmask, 0);
-			PROC_UNLOCK(p);
-		}
+		sigfastblock_resched(td, error == 0 && p->p_numthreads != 1);
+
 		break;
 
 	case SIGFASTBLOCK_UNSETPTR:
@@ -4079,7 +4092,6 @@ sys_sigfastblock(struct thread *td, struct sigfastbloc
 void
 sigfastblock_clear(struct thread *td)
 {
-	struct proc *p;
 	bool resched;
 
 	if ((td->td_pflags & TDP_SIGFASTBLOCK) == 0)
@@ -4088,12 +4100,7 @@ sigfastblock_clear(struct thread *td)
 	resched = (td->td_pflags & TDP_SIGFASTPENDING) != 0 ||
 	    SIGPENDING(td);
 	td->td_pflags &= ~(TDP_SIGFASTBLOCK | TDP_SIGFASTPENDING);
-	if (resched) {
-		p = td->td_proc;
-		PROC_LOCK(p);
-		reschedule_signals(p, td->td_sigmask, 0);
-		PROC_UNLOCK(p);
-	}
+	sigfastblock_resched(td, resched);
 }
 
 void