uio: we cannot mmap unaligned page contents

In commit 7314e613d5ff ("Fix a few incorrectly checked
[io_]remap_pfn_range() calls") the uio driver started more properly
checking the passed-in user mapping arguments against the size of the
actual uio driver data.

That in turn exposed that some driver authors apparently didn't realize
that mmap can only work on a page granularity, and had tried to use it
with smaller mappings, with the new size check catching that out.

So since it's not just the user mmap() arguments that can be confused,
make the uio mmap code also verify that the uio driver has the memory
allocated at page boundaries in order for mmap to work.  If the device
memory isn't properly aligned, we return

  [ENODEV]
    The fildes argument refers to a file whose type is not supported by mmap().

as per the open group documentation on mmap.

Reported-by: Holger Brunck <holger.brunck@keymile.com>
Acked-by: Greg KH <gregkh@linuxfoundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
index 67beb84449304d987c68a544c02b9c6e428dce1a..f7beb6eb40c714ae71309807b94b55a643501a9f 100644 (file)
--- a/drivers/uio/uio.c
+++ b/drivers/uio/uio.c
@@ -653,6 +653,8 @@ static int uio_mmap_physical(struct vm_area_struct *vma)
                return -EINVAL;
        mem = idev->info->mem + mi;
 
+       if (mem->addr & ~PAGE_MASK)
+               return -ENODEV;
        if (vma->vm_end - vma->vm_start > mem->size)
                return -EINVAL;