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Date:      Fri, 22 Aug 2014 08:19:08 +0000 (UTC)
From:      Konstantin Belousov <kib@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r270321 - head/sys/kern
Message-ID:  <201408220819.s7M8J8v0096257@svn.freebsd.org>
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Author: kib
Date: Fri Aug 22 08:19:08 2014
New Revision: 270321
URL: http://svnweb.freebsd.org/changeset/base/270321

Log:
  Ensure that sigaction flags for signal, which disposition is reset to
  ignored or default, are not leaking.  Apparently, there exists code
  which relies on SA_SIGINFO not reported for SIG_DFL or SIG_IGN.
  
  In kern_sigaction, ignore flags when resetting.  Encapsulate the flag
  and disposition testing into helper sigact_flag_test().
  
  On exec, and when delivering signal with SA_RESETHAND flag set,
  signals are reset automatically.  Use new helper sigdflt(), which
  removes duplicated code and corrects all flag bits for the signal.
  
  For proc0, set sigintr bit for all ignored signals.  Ignored signals
  are consumed in tdsendsignal() and not delivered to the victim thread
  at all.
  
  Reported and tested by:	royger
  Sponsored by:	The FreeBSD Foundation
  MFC after:	1 week

Modified:
  head/sys/kern/kern_sig.c

Modified: head/sys/kern/kern_sig.c
==============================================================================
--- head/sys/kern/kern_sig.c	Fri Aug 22 07:52:47 2014	(r270320)
+++ head/sys/kern/kern_sig.c	Fri Aug 22 08:19:08 2014	(r270321)
@@ -621,6 +621,15 @@ sig_ffs(sigset_t *set)
 	return (0);
 }
 
+static bool
+sigact_flag_test(struct sigaction *act, int flag)
+{
+
+	return ((act->sa_flags & flag) != 0 &&
+	    (__sighandler_t *)act->sa_sigaction != SIG_IGN &&
+	    (__sighandler_t *)act->sa_sigaction != SIG_DFL);
+}
+
 /*
  * kern_sigaction
  * sigaction
@@ -683,7 +692,7 @@ kern_sigaction(td, sig, act, oact, flags
 
 		ps->ps_catchmask[_SIG_IDX(sig)] = act->sa_mask;
 		SIG_CANTMASK(ps->ps_catchmask[_SIG_IDX(sig)]);
-		if (act->sa_flags & SA_SIGINFO) {
+		if (sigact_flag_test(act, SA_SIGINFO)) {
 			ps->ps_sigact[_SIG_IDX(sig)] =
 			    (__sighandler_t *)act->sa_sigaction;
 			SIGADDSET(ps->ps_siginfo, sig);
@@ -691,19 +700,19 @@ kern_sigaction(td, sig, act, oact, flags
 			ps->ps_sigact[_SIG_IDX(sig)] = act->sa_handler;
 			SIGDELSET(ps->ps_siginfo, sig);
 		}
-		if (!(act->sa_flags & SA_RESTART))
+		if (!sigact_flag_test(act, SA_RESTART))
 			SIGADDSET(ps->ps_sigintr, sig);
 		else
 			SIGDELSET(ps->ps_sigintr, sig);
-		if (act->sa_flags & SA_ONSTACK)
+		if (sigact_flag_test(act, SA_ONSTACK))
 			SIGADDSET(ps->ps_sigonstack, sig);
 		else
 			SIGDELSET(ps->ps_sigonstack, sig);
-		if (act->sa_flags & SA_RESETHAND)
+		if (sigact_flag_test(act, SA_RESETHAND))
 			SIGADDSET(ps->ps_sigreset, sig);
 		else
 			SIGDELSET(ps->ps_sigreset, sig);
-		if (act->sa_flags & SA_NODEFER)
+		if (sigact_flag_test(act, SA_NODEFER))
 			SIGADDSET(ps->ps_signodefer, sig);
 		else
 			SIGDELSET(ps->ps_signodefer, sig);
@@ -904,14 +913,36 @@ siginit(p)
 	PROC_LOCK(p);
 	ps = p->p_sigacts;
 	mtx_lock(&ps->ps_mtx);
-	for (i = 1; i <= NSIG; i++)
-		if (sigprop(i) & SA_IGNORE && i != SIGCONT)
+	for (i = 1; i <= NSIG; i++) {
+		if (sigprop(i) & SA_IGNORE && i != SIGCONT) {
 			SIGADDSET(ps->ps_sigignore, i);
+			SIGADDSET(ps->ps_sigintr, i);
+		}
+	}
 	mtx_unlock(&ps->ps_mtx);
 	PROC_UNLOCK(p);
 }
 
 /*
+ * Reset specified signal to the default disposition.
+ */
+static void
+sigdflt(struct sigacts *ps, int sig)
+{
+
+	mtx_assert(&ps->ps_mtx, MA_OWNED);
+	SIGDELSET(ps->ps_sigcatch, sig);
+	if ((sigprop(sig) & SA_IGNORE) != 0 && sig != SIGCONT)
+		SIGADDSET(ps->ps_sigignore, sig);
+	ps->ps_sigact[_SIG_IDX(sig)] = SIG_DFL;
+	SIGDELSET(ps->ps_siginfo, sig);
+	SIGADDSET(ps->ps_sigintr, sig);
+	SIGDELSET(ps->ps_sigonstack, sig);
+	SIGDELSET(ps->ps_sigreset, sig);
+	SIGDELSET(ps->ps_signodefer, sig);
+}
+
+/*
  * Reset signals for an exec of the specified process.
  */
 void
@@ -932,13 +963,9 @@ execsigs(struct proc *p)
 	mtx_lock(&ps->ps_mtx);
 	while (SIGNOTEMPTY(ps->ps_sigcatch)) {
 		sig = sig_ffs(&ps->ps_sigcatch);
-		SIGDELSET(ps->ps_sigcatch, sig);
-		if (sigprop(sig) & SA_IGNORE) {
-			if (sig != SIGCONT)
-				SIGADDSET(ps->ps_sigignore, sig);
+		sigdflt(ps, sig);
+		if ((sigprop(sig) & SA_IGNORE) != 0)
 			sigqueue_delete_proc(p, sig);
-		}
-		ps->ps_sigact[_SIG_IDX(sig)] = SIG_DFL;
 	}
 	/*
 	 * Reset stack state to the user stack.
@@ -1892,16 +1919,8 @@ trapsignal(struct thread *td, ksiginfo_t
 			SIGADDSET(mask, sig);
 		kern_sigprocmask(td, SIG_BLOCK, &mask, NULL,
 		    SIGPROCMASK_PROC_LOCKED | SIGPROCMASK_PS_LOCKED);
-		if (SIGISMEMBER(ps->ps_sigreset, sig)) {
-			/*
-			 * See kern_sigaction() for origin of this code.
-			 */
-			SIGDELSET(ps->ps_sigcatch, sig);
-			if (sig != SIGCONT &&
-			    sigprop(sig) & SA_IGNORE)
-				SIGADDSET(ps->ps_sigignore, sig);
-			ps->ps_sigact[_SIG_IDX(sig)] = SIG_DFL;
-		}
+		if (SIGISMEMBER(ps->ps_sigreset, sig))
+			sigdflt(ps, sig);
 		mtx_unlock(&ps->ps_mtx);
 	} else {
 		/*
@@ -2844,16 +2863,8 @@ postsig(sig)
 		kern_sigprocmask(td, SIG_BLOCK, &mask, NULL,
 		    SIGPROCMASK_PROC_LOCKED | SIGPROCMASK_PS_LOCKED);
 
-		if (SIGISMEMBER(ps->ps_sigreset, sig)) {
-			/*
-			 * See kern_sigaction() for origin of this code.
-			 */
-			SIGDELSET(ps->ps_sigcatch, sig);
-			if (sig != SIGCONT &&
-			    sigprop(sig) & SA_IGNORE)
-				SIGADDSET(ps->ps_sigignore, sig);
-			ps->ps_sigact[_SIG_IDX(sig)] = SIG_DFL;
-		}
+		if (SIGISMEMBER(ps->ps_sigreset, sig))
+			sigdflt(ps, sig);
 		td->td_ru.ru_nsignals++;
 		if (p->p_sig == sig) {
 			p->p_code = 0;

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