[PATCH] uml: fix fault handler on write

The UML fault handler was recently changed to enforce PROT_NONE protections,
by requiring VM_READ or VM_EXEC on VMA's.

However, by mistake, things were changed such that VM_READ is always checked,
also on write faults; so a VMA mapped with only PROT_WRITE is not readable
(unless it's prefaulted with MAP_POPULATE or with a write), which is different
from i386.

Discovered while testing remap_file_pages protection support.
Signed-off-by: NPaolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

arch/um/kernel/trap_kern.c

@@ -57,7 +57,8 @@ int handle_page_fault(unsigned long address, unsigned long ip,
 	if(is_write && !(vma->vm_flags & VM_WRITE)) 
 		goto out;
 
-        if(!(vma->vm_flags & (VM_READ | VM_EXEC)))
+	/* Don't require VM_READ|VM_EXEC for write faults! */
+        if(!is_write && !(vma->vm_flags & (VM_READ | VM_EXEC)))
                 goto out;
 
 	do {