flex_arrays: allow zero length flex arrays

commit bf69d41d198138e3c601e9a6645f4f1369aff7e0 upstream. Just like kmalloc will allow one to allocate a 0 length segment of memory flex arrays should do the same thing. It should bomb if you try to use something, but it should at least allow the allocation. This is needed because when SELinux switched to using flex_arrays in 2.6.38 the inability to allocate a 0 length array resulted in SELinux policy load returning -ENOSPC when previously it worked. Based-on-patch-by: Steffen Klassert <[email protected]> Signed-off-by: Eric Paris <[email protected]> Tested-by: Chris Richards <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]>
qsd8k-legacy · May 10, 2011 · aed7f28 · aed7f28
1 parent a201dc9
commit aed7f28
Showing 1 changed file with 10 additions and 1 deletion.
diff --git a/lib/flex_array.c b/lib/flex_array.c
@@ -253,9 +253,16 @@ int flex_array_prealloc(struct flex_array *fa, unsigned int start,
 	unsigned int end;
 	struct flex_array_part *part;
 
+	if (!start && !nr_elements)
+		return 0;
+	if (start >= fa->total_nr_elements)
+		return -ENOSPC;
+	if (!nr_elements)
+		return 0;
+
 	end = start + nr_elements - 1;
 
-	if (start >= fa->total_nr_elements || end >= fa->total_nr_elements)
+	if (end >= fa->total_nr_elements)
 		return -ENOSPC;
 	if (elements_fit_in_base(fa))
 		return 0;
@@ -346,6 +353,8 @@ int flex_array_shrink(struct flex_array *fa)
 	int part_nr;
 	int ret = 0;
 
+	if (!fa->total_nr_elements)
+		return 0;
 	if (elements_fit_in_base(fa))
 		return ret;
 	for (part_nr = 0; part_nr < FLEX_ARRAY_NR_BASE_PTRS; part_nr++) {