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 <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Cc: Rik van Riel <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 01e6b614839d3be030658eed24fa05eb3268c540..10a8c6da385fc5dcae4105e4eeefe3440eabb91d 100644 (file)
--- 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