mm: fail GFP_DMA allocations when ZONE_DMA is not configured

The page allocator will improperly return a page from ZONE_NORMAL even
when __GFP_DMA is passed if CONFIG_ZONE_DMA is disabled.  The caller
expects DMA memory, perhaps for ISA devices with 16-bit address registers,
and may get higher memory resulting in undefined behavior.

This patch causes the page allocator to return NULL in such circumstances
with a warning emitted to the kernel log on the first occurrence.

Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 01e6b614839d..10a8c6da385f 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2247,6 +2247,10 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
 
         if (should_fail_alloc_page(gfp_mask, order))
                 return NULL;
+#ifndef CONFIG_ZONE_DMA
+        if (WARN_ON_ONCE(gfp_mask & __GFP_DMA))
+                return NULL;
+#endif
 
         /*
          * Check the zones suitable for the gfp_mask contain at least one