mm: make vb_alloc() more foolproof

If someone calls vb_alloc() (or vm_map_ram() for that matter) to allocate 0 bytes (0 pages), get_order() returns BITS_PER_LONG - PAGE_CACHE_SHIFT and interesting stuff happens. So make debugging such problems easier and warn about 0-size allocation. [[email protected]: use WARN_ON-return-value feature] Signed-off-by: Jan Kara <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
bobihu · Aug 1, 2012 · aa91c4d · aa91c4d
1 parent 92ca922
commit aa91c4d
Showing 1 changed file with 8 additions and 0 deletions.
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
@@ -904,6 +904,14 @@ static void *vb_alloc(unsigned long size, gfp_t gfp_mask)
 
 	BUG_ON(size & ~PAGE_MASK);
 	BUG_ON(size > PAGE_SIZE*VMAP_MAX_ALLOC);
+	if (WARN_ON(size == 0)) {
+		/*
+		 * Allocating 0 bytes isn't what caller wants since
+		 * get_order(0) returns funny result. Just warn and terminate
+		 * early.
+		 */
+		return NULL;
+	}
 	order = get_order(size);
 
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