mm/cma.c: check the max limit for cma allocation

CMA allocation request size is represented by size_t that gets truncated when same is passed as int to bitmap_find_next_zero_area_off. We observe that during fuzz testing when cma allocation request is too high, bitmap_find_next_zero_area_off still returns success due to the truncation. This leads to kernel crash, as subsequent code assumes that requested memory is available. Fail cma allocation in case the request breaches the corresponding cma region size. Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Shiraz Hashim <[email protected]> Cc: Catalin Marinas <[email protected]> Cc: Stephen Rothwell <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
chewitt · Nov 11, 2016 · 6b36ba5 · 6b36ba5
1 parent eef06b8
commit 6b36ba5
Showing 1 changed file with 3 additions and 0 deletions.
diff --git a/mm/cma.c b/mm/cma.c
@@ -385,6 +385,9 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align)
 	bitmap_maxno = cma_bitmap_maxno(cma);
 	bitmap_count = cma_bitmap_pages_to_bits(cma, count);
 
+	if (bitmap_count > bitmap_maxno)
+		return NULL;
+
 	for (;;) {
 		mutex_lock(&cma->lock);
 		bitmap_no = bitmap_find_next_zero_area_off(cma->bitmap,