vm audit: add VM_DONTEXPAND to mmap for drivers that need it

Drivers that register a ->fault handler, but do not range-check the
offset argument, must set VM_DONTEXPAND in the vm_flags in order to
prevent an expanding mremap from overflowing the resource.

I've audited the tree and attempted to fix these problems (usually by
adding VM_DONTEXPAND where it is not obvious).

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 8 deletions

diff --git a/sound/oss/via82cxxx_audio.c b/sound/oss/via82cxxx_audio.c
index 5d3c0372df32..f95aa0946758 100644
--- a/sound/oss/via82cxxx_audio.c
+++ b/sound/oss/via82cxxx_audio.c
@@ -2104,6 +2104,7 @@ static struct page * via_mm_nopage (struct vm_area_struct * vma,
 {
         struct via_info *card = vma->vm_private_data;
         struct via_channel *chan = &card->ch_out;
+        unsigned long max_bufs;
         struct page *dmapage;
         unsigned long pgoff;
         int rd, wr;
@@ -2127,14 +2128,11 @@ static struct page * via_mm_nopage (struct vm_area_struct * vma,
         rd = card->ch_in.is_mapped;
         wr = card->ch_out.is_mapped;
 
-#ifndef VIA_NDEBUG
-        {
-        unsigned long max_bufs = chan->frag_number;
-        if (rd && wr) max_bufs *= 2;
-        /* via_dsp_mmap() should ensure this */
-        assert (pgoff < max_bufs);
-        }
-#endif
+        max_bufs = chan->frag_number;
+        if (rd && wr)
+                max_bufs *= 2;
+        if (pgoff >= max_bufs)
+                return NOPAGE_SIGBUS;
 
         /* if full-duplex (read+write) and we have two sets of bufs,
          * then the playback buffers come first, sez soundcard.c */