As noted in the "Deprecated Interfaces, Language Features, Attributes,
and Conventions" documentation [1], size calculations (especially
multiplication) should not be performed in memory allocator (or similar)
function arguments due to the risk of them overflowing. This could lead
to values wrapping around and a smaller allocation being made than the
caller was expecting. Using those allocations could lead to linear
overflows of heap memory and other misbehaviors.
So, use the struct_size() helper to do the arithmetic instead of the
argument "size + count * size" in the kvmalloc() functions.
Also, take the opportunity to refactor the memcpy() call to use the
flex_array_size() helper.
This code was detected with the help of Coccinelle and audited and fixed
manually.
[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
Signed-off-by: Len Baker <[email protected]>
---
Hi,
this patch is built against the linux-next tree (tag next-20211015).
Regards,
Len
mm/list_lru.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/mm/list_lru.c b/mm/list_lru.c
index cd58790d0fb3..a6031f1c5bd7 100644
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -354,8 +354,7 @@ static int memcg_init_list_lru_node(struct list_lru_node *nlru)
struct list_lru_memcg *memcg_lrus;
int size = memcg_nr_cache_ids;
- memcg_lrus = kvmalloc(sizeof(*memcg_lrus) +
- size * sizeof(void *), GFP_KERNEL);
+ memcg_lrus = kvmalloc(struct_size(memcg_lrus, lru, size), GFP_KERNEL);
if (!memcg_lrus)
return -ENOMEM;
@@ -389,7 +388,7 @@ static int memcg_update_list_lru_node(struct list_lru_node *nlru,
old = rcu_dereference_protected(nlru->memcg_lrus,
lockdep_is_held(&list_lrus_mutex));
- new = kvmalloc(sizeof(*new) + new_size * sizeof(void *), GFP_KERNEL);
+ new = kvmalloc(struct_size(new, lru, new_size), GFP_KERNEL);
if (!new)
return -ENOMEM;
@@ -398,7 +397,7 @@ static int memcg_update_list_lru_node(struct list_lru_node *nlru,
return -ENOMEM;
}
- memcpy(&new->lru, &old->lru, old_size * sizeof(void *));
+ memcpy(&new->lru, &old->lru, flex_array_size(new, lru, old_size));
/*
* The locking below allows readers that hold nlru->lock avoid taking
--
2.25.1