flex_arrays: allow zero length flex arrays

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]> Cc: [email protected] [2.6.38+]
jic23 · Apr 28, 2011 · bf69d41 · bf69d41
1 parent 5d30b10
commit bf69d41
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++) {