Properly copy the P_ALTSTACK flag in struct proc::p_flag to the child

process on fork(2).

It is the supposed behavior stated in the manpage of sigaction(2), and
Solaris, NetBSD and FreeBSD 3-STABLE correctly do so.

The previous fix against libc_r/uthread/uthread_fork.c fixed the
problem only for the programs linked with libc_r, so back it out and
fix fork(2) itself to help those not linked with libc_r as well.

PR:		kern/26705
Submitted by:	KUROSAWA Takahiro <fwkg7679@mb.infoweb.ne.jp>
Tested by:	knu, GOTOU Yuuzou <gotoyuzo@notwork.org>,
		and some other people
Not objected by:	hackers
MFC in:		3 days

5 files changed, 5 insertions, 34 deletions

diff --git a/lib/libc_r/uthread/uthread_fork.c b/lib/libc_r/uthread/uthread_fork.c
index a2aabbe..4437d88 100644
--- a/lib/libc_r/uthread/uthread_fork.c
+++ b/lib/libc_r/uthread/uthread_fork.c
@@ -32,7 +32,6 @@
  * $FreeBSD$
  */
 #include <errno.h>
-#include <signal.h>
 #include <string.h>
 #include <stdlib.h>
 #include <unistd.h>
@@ -113,16 +112,7 @@ _fork(void)
 		else if (_pq_init(&_readyq) != 0) {
 			/* Abort this application: */
 			PANIC("Cannot initialize priority ready queue.");
-		} else if ((_thread_sigstack.ss_sp == NULL) &&
-		    ((_thread_sigstack.ss_sp = malloc(SIGSTKSZ)) == NULL))
-			PANIC("Unable to allocate alternate signal stack");
-		else {
-			/* Install the alternate signal stack: */
-			_thread_sigstack.ss_size = SIGSTKSZ;
-			_thread_sigstack.ss_flags = 0;
-			if (__sys_sigaltstack(&_thread_sigstack, NULL) != 0)
-				PANIC("Unable to install alternate signal stack");
-
+		} else {
 			/*
 			 * Enter a loop to remove all threads other than
 			 * the running thread from the thread list:
diff --git a/lib/libkse/thread/thr_fork.c b/lib/libkse/thread/thr_fork.c
index a2aabbe..4437d88 100644
--- a/lib/libkse/thread/thr_fork.c
+++ b/lib/libkse/thread/thr_fork.c
@@ -32,7 +32,6 @@
  * $FreeBSD$
  */
 #include <errno.h>
-#include <signal.h>
 #include <string.h>
 #include <stdlib.h>
 #include <unistd.h>
@@ -113,16 +112,7 @@ _fork(void)
 		else if (_pq_init(&_readyq) != 0) {
 			/* Abort this application: */
 			PANIC("Cannot initialize priority ready queue.");
-		} else if ((_thread_sigstack.ss_sp == NULL) &&
-		    ((_thread_sigstack.ss_sp = malloc(SIGSTKSZ)) == NULL))
-			PANIC("Unable to allocate alternate signal stack");
-		else {
-			/* Install the alternate signal stack: */
-			_thread_sigstack.ss_size = SIGSTKSZ;
-			_thread_sigstack.ss_flags = 0;
-			if (__sys_sigaltstack(&_thread_sigstack, NULL) != 0)
-				PANIC("Unable to install alternate signal stack");
-
+		} else {
 			/*
 			 * Enter a loop to remove all threads other than
 			 * the running thread from the thread list:
diff --git a/lib/libpthread/thread/thr_fork.c b/lib/libpthread/thread/thr_fork.c
index a2aabbe..4437d88 100644
--- a/lib/libpthread/thread/thr_fork.c
+++ b/lib/libpthread/thread/thr_fork.c
@@ -32,7 +32,6 @@
  * $FreeBSD$
  */
 #include <errno.h>
-#include <signal.h>
 #include <string.h>
 #include <stdlib.h>
 #include <unistd.h>
@@ -113,16 +112,7 @@ _fork(void)
 		else if (_pq_init(&_readyq) != 0) {
 			/* Abort this application: */
 			PANIC("Cannot initialize priority ready queue.");
-		} else if ((_thread_sigstack.ss_sp == NULL) &&
-		    ((_thread_sigstack.ss_sp = malloc(SIGSTKSZ)) == NULL))
-			PANIC("Unable to allocate alternate signal stack");
-		else {
-			/* Install the alternate signal stack: */
-			_thread_sigstack.ss_size = SIGSTKSZ;
-			_thread_sigstack.ss_flags = 0;
-			if (__sys_sigaltstack(&_thread_sigstack, NULL) != 0)
-				PANIC("Unable to install alternate signal stack");
-
+		} else {
 			/*
 			 * Enter a loop to remove all threads other than
 			 * the running thread from the thread list:
diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c
index c9539bb..d3b991d 100644
--- a/sys/kern/kern_fork.c
+++ b/sys/kern/kern_fork.c
@@ -495,7 +495,7 @@ again:
 	 * Preserve some more flags in subprocess.  PS_PROFIL has already
 	 * been preserved.
 	 */
-	p2->p_flag |= p1->p_flag & P_SUGID;
+	p2->p_flag |= p1->p_flag & (P_SUGID | P_ALTSTACK);
 	if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
 		p2->p_flag |= P_CONTROLT;
 	if (flags & RFPPWAIT)
diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
index c57074a..55da023 100644
--- a/sys/kern/kern_sig.c
+++ b/sys/kern/kern_sig.c
@@ -464,6 +464,7 @@ execsigs(p)
 	p->p_sigstk.ss_flags = SS_DISABLE;
 	p->p_sigstk.ss_size = 0;
 	p->p_sigstk.ss_sp = 0;
+	p->p_flag &= ~P_ALTSTACK;
 	/*
 	 * Reset no zombies if child dies flag as Solaris does.
 	 */