flex_array: poison free elements
Newly initialized flex_array's and/or flex_array_part's are now poisoned
with a new poison value, FLEX_ARRAY_FREE. It's value is similar to
POISON_FREE used in the various slab allocators, but is different to
distinguish between flex array's poisoned kmem and slab allocator poisoned
kmem.
This will allow us to identify flex_array_part's that only contain free
elements (and free them with an addition to the flex_array API). This
could also be extended in the future to identify `get' uses on elements
that have not been `put'.
If __GFP_ZERO is passed for a part's gfp mask, the poisoning is avoided.
These elements are considered to be in-use since they have been
initialized.
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/lib/flex_array.c b/lib/flex_array.c
index b68f99b..e22d0e9 100644
--- a/lib/flex_array.c
+++ b/lib/flex_array.c
@@ -113,6 +113,8 @@
return NULL;
ret->element_size = element_size;
ret->total_nr_elements = total;
+ if (elements_fit_in_base(ret) && !(flags & __GFP_ZERO))
+ memset(ret->parts[0], FLEX_ARRAY_FREE, bytes_left_in_base());
return ret;
}
@@ -159,15 +161,12 @@
{
struct flex_array_part *part = fa->parts[part_nr];
if (!part) {
- /*
- * This leaves the part pages uninitialized
- * and with potentially random data, just
- * as if the user had kmalloc()'d the whole.
- * __GFP_ZERO can be used to zero it.
- */
- part = kmalloc(FLEX_ARRAY_PART_SIZE, flags);
+ part = kmalloc(sizeof(struct flex_array_part), flags);
if (!part)
return NULL;
+ if (!(flags & __GFP_ZERO))
+ memset(part, FLEX_ARRAY_FREE,
+ sizeof(struct flex_array_part));
fa->parts[part_nr] = part;
}
return part;
@@ -228,7 +227,7 @@
return -EINVAL;
}
dst = &part->elements[index_inside_part(fa, element_nr)];
- memset(dst, 0, fa->element_size);
+ memset(dst, FLEX_ARRAY_FREE, fa->element_size);
return 0;
}