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SubjectRe: More info for DSM w/r/t sunffb on 2.6.15-rc6
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From: Linus Torvalds <torvalds@osdl.org>
Date: Sat, 24 Dec 2005 00:32:26 -0800 (PST)

> On Fri, 23 Dec 2005, David S. Miller wrote:
> > + if (!(vma->vm_flags & VM_SHARED))
> > + return -EINVAL;
> > +
>
> Side note - as I explained to Nick the other week, VM_SHARED really means
> "shared _writable_" mapping, so you're now disallowing a shared read-only
> open too.
>
> Which may be fine, of course. Especially if sbusfb always ends up giving a
> writable pfn-mapping. But I wanted to check that that was what you meant
> to do.
>
> To test for MAP_SHARED, either do the is_cow_mapping() thing, or check
> the VM_MAYSHARE bit.

I did mean to test for MAP_SHARED, thanks for the test.
I've made the check like this:

diff --git a/drivers/video/sbuslib.c b/drivers/video/sbuslib.c
index 646c43f..3a74a63 100644
--- a/drivers/video/sbuslib.c
+++ b/drivers/video/sbuslib.c
@@ -46,6 +46,9 @@ int sbusfb_mmap_helper(struct sbus_mmap_
unsigned long off;
int i;

+ if (!(vma->vm_flags & (VM_SHARED | VM_MAYSHARE)))
+ return -EINVAL;
+
size = vma->vm_end - vma->vm_start;
if (vma->vm_pgoff > (~0UL >> PAGE_SHIFT))
return -EINVAL;
-
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