diff -urN 2.3.99-pre4-pre2/arch/alpha/mm/fault.c user-stack-overflow/arch/alpha/mm/fault.c
--- 2.3.99-pre4-pre2/arch/alpha/mm/fault.c	Fri Mar  3 02:19:23 2000
+++ user-stack-overflow/arch/alpha/mm/fault.c	Sat Apr  1 18:27:55 2000
@@ -115,7 +115,7 @@
 		goto good_area;
 	if (!(vma->vm_flags & VM_GROWSDOWN))
 		goto bad_area;
-	if (expand_stack(vma, address))
+	if (expand_stack(vma, address, NULL))
 		goto bad_area;
 /*
  * Ok, we have a good vm_area for this memory access, so
diff -urN 2.3.99-pre4-pre2/arch/i386/mm/fault.c user-stack-overflow/arch/i386/mm/fault.c
--- 2.3.99-pre4-pre2/arch/i386/mm/fault.c	Sun Jan 30 15:43:27 2000
+++ user-stack-overflow/arch/i386/mm/fault.c	Sat Apr  1 18:28:37 2000
@@ -30,13 +30,13 @@
  */
 int __verify_write(const void * addr, unsigned long size)
 {
-	struct vm_area_struct * vma;
+	struct vm_area_struct * vma, * prev_vma;
 	unsigned long start = (unsigned long) addr;
 
 	if (!size)
 		return 1;
 
-	vma = find_vma(current->mm, start);
+	vma = find_vma_prev(current->mm, start, &prev_vma);
 	if (!vma)
 		goto bad_area;
 	if (vma->vm_start > start)
@@ -70,7 +70,7 @@
 check_stack:
 	if (!(vma->vm_flags & VM_GROWSDOWN))
 		goto bad_area;
-	if (expand_stack(vma, start) == 0)
+	if (expand_stack(vma, start, prev_vma) == 0)
 		goto good_area;
 
 bad_area:
@@ -119,7 +119,7 @@
 {
 	struct task_struct *tsk;
 	struct mm_struct *mm;
-	struct vm_area_struct * vma;
+	struct vm_area_struct * vma, * prev_vma;
 	unsigned long address;
 	unsigned long page;
 	unsigned long fixup;
@@ -141,7 +141,7 @@
 
 	down(&mm->mmap_sem);
 
-	vma = find_vma(mm, address);
+	vma = find_vma_prev(mm, address, &prev_vma);
 	if (!vma)
 		goto bad_area;
 	if (vma->vm_start <= address)
@@ -158,7 +158,7 @@
 		if (address + 32 < regs->esp)
 			goto bad_area;
 	}
-	if (expand_stack(vma, address))
+	if (expand_stack(vma, address, prev_vma))
 		goto bad_area;
 /*
  * Ok, we have a good vm_area for this memory access, so
diff -urN 2.3.99-pre4-pre2/arch/ppc/mm/fault.c user-stack-overflow/arch/ppc/mm/fault.c
--- 2.3.99-pre4-pre2/arch/ppc/mm/fault.c	Fri Mar 31 05:30:19 2000
+++ user-stack-overflow/arch/ppc/mm/fault.c	Sat Apr  1 18:27:55 2000
@@ -60,7 +60,7 @@
 void do_page_fault(struct pt_regs *regs, unsigned long address,
 		   unsigned long error_code)
 {
-	struct vm_area_struct * vma;
+	struct vm_area_struct * vma, * prev_vma;
 	struct mm_struct *mm = current->mm;
 #if defined(CONFIG_4xx)
 	int is_write = error_code & ESR_DST;
@@ -96,14 +96,14 @@
 		return;
 	}
 	down(&mm->mmap_sem);
-	vma = find_vma(mm, address);
+	vma = find_vma_prev(mm, address, &prev_vma);
 	if (!vma)
 		goto bad_area;
 	if (vma->vm_start <= address)
 		goto good_area;
 	if (!(vma->vm_flags & VM_GROWSDOWN))
 		goto bad_area;
-	if (expand_stack(vma, address))
+	if (expand_stack(vma, address, prev_vma))
 		goto bad_area;
 
 good_area:
diff -urN 2.3.99-pre4-pre2/include/linux/mm.h user-stack-overflow/include/linux/mm.h
--- 2.3.99-pre4-pre2/include/linux/mm.h	Fri Mar 31 05:30:20 2000
+++ user-stack-overflow/include/linux/mm.h	Sat Apr  1 18:27:55 2000
@@ -491,13 +491,18 @@
 
 #define GFP_HIGHMEM	__GFP_HIGHMEM
 
+extern int heap_stack_gap;
+
 /* vma is the first one with  address < vma->vm_end,
  * and even  address < vma->vm_start. Have to extend vma. */
-static inline int expand_stack(struct vm_area_struct * vma, unsigned long address)
+static inline int expand_stack(struct vm_area_struct * vma, unsigned long address,
+			       struct vm_area_struct * prev_vma)
 {
 	unsigned long grow;
 
 	address &= PAGE_MASK;
+	if (prev_vma && prev_vma->vm_end + (heap_stack_gap << PAGE_SHIFT) > address)
+		return -ENOMEM;
 	grow = (vma->vm_start - address) >> PAGE_SHIFT;
 	if (vma->vm_end - address > current->rlim[RLIMIT_STACK].rlim_cur ||
 	    ((vma->vm_mm->total_vm + grow) << PAGE_SHIFT) > current->rlim[RLIMIT_AS].rlim_cur)
diff -urN 2.3.99-pre4-pre2/include/linux/sysctl.h user-stack-overflow/include/linux/sysctl.h
--- 2.3.99-pre4-pre2/include/linux/sysctl.h	Sat Mar 11 20:02:33 2000
+++ user-stack-overflow/include/linux/sysctl.h	Sat Apr  1 18:27:55 2000
@@ -127,7 +127,8 @@
 	VM_PAGECACHE=7,		/* struct: Set cache memory thresholds */
 	VM_PAGERDAEMON=8,	/* struct: Control kswapd behaviour */
 	VM_PGT_CACHE=9,		/* struct: Set page table cache parameters */
-	VM_PAGE_CLUSTER=10	/* int: set number of pages to swap together */
+	VM_PAGE_CLUSTER=10,	/* int: set number of pages to swap together */
+	VM_HEAP_STACK_GAP=11,	/* int: page gap between heap and stack */
 };
 
 
diff -urN 2.3.99-pre4-pre2/kernel/sysctl.c user-stack-overflow/kernel/sysctl.c
--- 2.3.99-pre4-pre2/kernel/sysctl.c	Mon Mar 27 22:44:50 2000
+++ user-stack-overflow/kernel/sysctl.c	Sat Apr  1 18:27:55 2000
@@ -243,6 +243,8 @@
 	 &pgt_cache_water, 2*sizeof(int), 0600, NULL, &proc_dointvec},
 	{VM_PAGE_CLUSTER, "page-cluster", 
 	 &page_cluster, sizeof(int), 0600, NULL, &proc_dointvec},
+	{VM_HEAP_STACK_GAP, "heap-stack-gap", 
+	 &heap_stack_gap, sizeof(int), 0644, NULL, &proc_dointvec},
 	{0}
 };
 
diff -urN 2.3.99-pre4-pre2/mm/memory.c user-stack-overflow/mm/memory.c
--- 2.3.99-pre4-pre2/mm/memory.c	Mon Mar 27 22:44:50 2000
+++ user-stack-overflow/mm/memory.c	Sat Apr  1 18:28:57 2000
@@ -457,13 +457,14 @@
 	 */
 	while (ptr < end) {
 		if (!vma || ptr >= vma->vm_end) {
-			vma = find_vma(current->mm, ptr);
+			struct vm_area_struct * prev_vma;
+			vma = find_vma_prev(current->mm, ptr, &prev_vma);
 			if (!vma) 
 				goto out_unlock;
 			if (vma->vm_start > ptr) {
 				if (!(vma->vm_flags & VM_GROWSDOWN))
 					goto out_unlock;
-				if (expand_stack(vma, ptr))
+				if (expand_stack(vma, ptr, prev_vma))
 					goto out_unlock;
 			}
 			if (((datain) && (!(vma->vm_flags & VM_WRITE))) ||
diff -urN 2.3.99-pre4-pre2/mm/mmap.c user-stack-overflow/mm/mmap.c
--- 2.3.99-pre4-pre2/mm/mmap.c	Mon Mar 27 22:44:50 2000
+++ user-stack-overflow/mm/mmap.c	Sat Apr  1 18:27:55 2000
@@ -40,6 +40,7 @@
 kmem_cache_t *vm_area_cachep;
 
 int sysctl_overcommit_memory;
+int heap_stack_gap = 128;
 
 /* Check that a process has enough memory to allocate a
  * new virtual mapping.
@@ -365,9 +366,14 @@
 
 	for (vmm = find_vma(current->mm, addr); ; vmm = vmm->vm_next) {
 		/* At this point:  (!vmm || addr < vmm->vm_end). */
+		unsigned long __heap_stack_gap = 0;
 		if (TASK_SIZE - len < addr)
 			return 0;
-		if (!vmm || addr + len <= vmm->vm_start)
+		if (!vmm)
+			return addr;
+		if (vmm->vm_flags & VM_GROWSDOWN)
+			__heap_stack_gap = heap_stack_gap << PAGE_SHIFT;
+		if (addr + len + __heap_stack_gap <= vmm->vm_start)
 			return addr;
 		addr = vmm->vm_end;
 	}
@@ -470,11 +476,11 @@
 
 struct vm_area_struct * find_extend_vma(struct task_struct * tsk, unsigned long addr)
 {
-	struct vm_area_struct * vma;
+	struct vm_area_struct * vma, * prev_vma;
 	unsigned long start;
 
 	addr &= PAGE_MASK;
-	vma = find_vma(tsk->mm,addr);
+	vma = find_vma_prev(tsk->mm,addr, &prev_vma);
 	if (!vma)
 		return NULL;
 	if (vma->vm_start <= addr)
@@ -482,7 +488,7 @@
 	if (!(vma->vm_flags & VM_GROWSDOWN))
 		return NULL;
 	start = vma->vm_start;
-	if (expand_stack(vma, addr))
+	if (expand_stack(vma, addr, prev_vma))
 		return NULL;
 	if (vma->vm_flags & VM_LOCKED) {
 		make_pages_present(addr, start);