From: Len Baker <len.baker@gmx.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Len Baker <len.baker@gmx.com>, Kees Cook <keescook@chromium.org>,
"Gustavo A. R. Silva" <gustavoars@kernel.org>,
linux-hardening@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: [PATCH] mm/list_lru.c: prefer struct_size over open coded arithmetic
Date: Sun, 17 Oct 2021 12:59:29 +0200 [thread overview]
Message-ID: <20211017105929.9284-1-len.baker@gmx.com> (raw)
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 <len.baker@gmx.com>
---
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
reply other threads:[~2021-10-17 11:00 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20211017105929.9284-1-len.baker@gmx.com \
--to=len.baker@gmx.com \
--cc=akpm@linux-foundation.org \
--cc=gustavoars@kernel.org \
--cc=keescook@chromium.org \
--cc=linux-hardening@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).