From 0fd52730c216aa70c9761b100b73f0ec0ffab6ea Mon Sep 17 00:00:00 2001
From: bde <bde@FreeBSD.org>
Date: Tue, 2 Feb 1999 12:11:01 +0000
Subject: Switch context before doing some i/o operations that might block if
 context would be switched on return to user mode.  This fixes some denial of
 service problems.

---
 sys/kern/kern_subr.c | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

(limited to 'sys/kern')

diff --git a/sys/kern/kern_subr.c b/sys/kern/kern_subr.c
index a96d554..d8e1f08 100644
--- a/sys/kern/kern_subr.c
+++ b/sys/kern/kern_subr.c
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)kern_subr.c	8.3 (Berkeley) 1/21/94
- * $Id: kern_subr.c,v 1.23 1999/01/08 17:31:10 eivind Exp $
+ * $Id: kern_subr.c,v 1.24 1999/01/10 01:58:24 eivind Exp $
  */
 
 #include <sys/param.h>
@@ -44,6 +44,7 @@
 #include <sys/proc.h>
 #include <sys/malloc.h>
 #include <sys/lock.h>
+#include <sys/resourcevar.h>
 #include <sys/vnode.h>
 
 #include <vm/vm.h>
@@ -51,6 +52,10 @@
 #include <vm/vm_page.h>
 #include <vm/vm_map.h>
 
+#include <machine/cpu.h>
+
+static void	uio_yield __P((void));
+
 int
 uiomove(cp, n, uio)
 	register caddr_t cp;
@@ -81,6 +86,8 @@ uiomove(cp, n, uio)
 
 		case UIO_USERSPACE:
 		case UIO_USERISPACE:
+			if (resched_wanted())
+				uio_yield();
 			if (uio->uio_rw == UIO_READ)
 				error = copyout(cp, iov->iov_base, cnt);
 			else
@@ -139,6 +146,8 @@ uiomoveco(cp, n, uio, obj)
 
 		case UIO_USERSPACE:
 		case UIO_USERISPACE:
+			if (resched_wanted())
+				uio_yield();
 			if (uio->uio_rw == UIO_READ) {
 				if (vfs_ioopt && ((cnt & PAGE_MASK) == 0) &&
 					((((intptr_t) iov->iov_base) & PAGE_MASK) == 0) &&
@@ -214,6 +223,8 @@ uioread(n, uio, obj, nread)
 
 			cnt &= ~PAGE_MASK;
 
+			if (resched_wanted())
+				uio_yield();
 			error = vm_uiomove(&curproc->p_vmspace->vm_map, obj,
 						uio->uio_offset, cnt,
 						(vm_offset_t) iov->iov_base, &npagesmoved);
@@ -389,3 +400,17 @@ phashinit(elements, type, nentries)
 	*nentries = hashsize;
 	return (hashtbl);
 }
+
+static void
+uio_yield()
+{
+	struct proc *p;
+	int s;
+
+	p = curproc;
+	s = splhigh();
+	setrunqueue(p);
+	p->p_stats->p_ru.ru_nivcsw++;
+	mi_switch();
+	splx(s);
+}
-- 
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