From: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Date: Sat, 10 Sep 2005 17:44:57 +0000 (+0200)
Subject: [PATCH] uml: fix fault handler on write
X-Git-Tag: v2.6.14-rc1~131
X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=d129f31236c241c07e583e8bc695c382365d02ce;p=linux-2.6-omap-h63xx.git

[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: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---

diff --git a/arch/um/kernel/trap_kern.c b/arch/um/kernel/trap_kern.c
index b5fc89fe9ea..d20361dcd12 100644
--- a/arch/um/kernel/trap_kern.c
+++ b/arch/um/kernel/trap_kern.c
@@ -57,7 +57,8 @@ good_area:
 	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 {