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[PATCH] NOMMU: Check VMA protections

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Check the VMA protections in get_user_pages() against what's being asked.

This checks to see that we don't accidentally write on a non-writable VMA or
permit an I/O mapping VMA to be accessed (which may lack page structs).

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
David Howells 2006-09-27 01:50:18 -07:00 committed by Linus Torvalds
parent 910e46da4b
commit 7b4d5b8b39
1 changed files with 25 additions and 5 deletions
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30
mm/nommu.c
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@ -122,19 +122,35 @@ unsigned int kobjsize(const void *objp)
}
/*
* The nommu dodgy version :-)
* get a list of pages in an address range belonging to the specified process
* and indicate the VMA that covers each page
* - this is potentially dodgy as we may end incrementing the page count of a
* slab page or a secondary page from a compound page
* - don't permit access to VMAs that don't support it, such as I/O mappings
*/
int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
unsigned long start, int len, int write, int force,
struct page **pages, struct vm_area_struct **vmas)
{
int i;
struct vm_area_struct *vma;
unsigned long vm_flags;
int i;
/* calculate required read or write permissions.
* - if 'force' is set, we only require the "MAY" flags.
*/
vm_flags = write ? (VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
vm_flags &= force ? (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
for (i = 0; i < len; i++) {
vma = find_vma(mm, start);
if(!vma)
return i ? : -EFAULT;
if (!vma)
goto finish_or_fault;
/* protect what we can, including chardevs */
if (vma->vm_flags & (VM_IO | VM_PFNMAP) ||
!(vm_flags & vma->vm_flags))
goto finish_or_fault;
if (pages) {
pages[i] = virt_to_page(start);
@ -145,7 +161,11 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
vmas[i] = vma;
start += PAGE_SIZE;
}
return(i);
return i;
finish_or_fault:
return i ? : -EFAULT;
}
EXPORT_SYMBOL(get_user_pages);