From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Gustavo A. R. Silva" Subject: [PATCH v3][next] cgroup: Avoid -Wstringop-overflow warnings Date: Thu, 17 Aug 2023 11:19:13 -0600 Message-ID: Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1692292692; bh=PUtRgHl3t9y/PCdYajGwcmizA+UGYBohYR7AEs0pjoo=; h=Date:From:To:Cc:Subject:From; b=qrg+XKqtRmV4/lmX29QP+7xjp0iql30uzjiD/+IZf66y5T9KcdewLTYZLNPMLLHyM zZuOu2SBecnTFBGa+i5d8VK1GcTirNqkjHGiCHxy0AtS5/VasEbdKajh/kCrAhRnB0 ENAHlyX5uztjNp2p+SMQATfNTA0AjNScQgDEWtxMjBJs0Nfn9AgMsEYjz6kE4bNIOq cTF8302WgmW7xV7ayZzahJqkK2AT4OyN83DHtmaVZKbBwHcMOuAe5RmpNWN6yLRzw3 HOiC+2xAbd3s9kXKmpB+C/kqsS3s5VE9PLJWxVPFgyuO30dXs6ROSxF9HEwlIKjFta iH27n6fLi5eIg== Content-Disposition: inline List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Tejun Heo , Zefan Li , Johannes Weiner Cc: cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, "Gustavo A. R. Silva" , linux-hardening-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Change the notation from pointer-to-array to pointer-to-pointer. With this, we avoid the compiler complaining about trying to access a region of size zero as an argument during function calls. This is a workaround to prevent the compiler complaining about accessing an array of size zero when evaluating the arguments of a couple of function calls. See below: kernel/cgroup/cgroup.c: In function 'find_css_set': kernel/cgroup/cgroup.c:1206:16: warning: 'find_existing_css_set' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] 1206 | cset = find_existing_css_set(old_cset, cgrp, template); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ kernel/cgroup/cgroup.c:1206:16: note: referencing argument 3 of type 'struct cgroup_subsys_state *[0]' kernel/cgroup/cgroup.c:1071:24: note: in a call to function 'find_existing_css_set' 1071 | static struct css_set *find_existing_css_set(struct css_set *old_cset, | ^~~~~~~~~~~~~~~~~~~~~ With the change to pointer-to-pointer, the functions are not prevented from being executed, and they will do what they have to do when CGROUP_SUBSYS_COUNT == 0. Address the following -Wstringop-overflow warnings seen when built with ARM architecture and aspeed_g4_defconfig configuration (notice that under this configuration CGROUP_SUBSYS_COUNT == 0): kernel/cgroup/cgroup.c:1208:16: warning: 'find_existing_css_set' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] kernel/cgroup/cgroup.c:1258:15: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] kernel/cgroup/cgroup.c:6089:18: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] kernel/cgroup/cgroup.c:6153:18: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] This results in no differences in binary output. Link: https://github.com/KSPP/linux/issues/316 Signed-off-by: Gustavo A. R. Silva --- Changes in v3: - Update changelog text to point out that this is a workaround. Changes in v2: - Use pointer-to-pointer instead of pointer-to-array. - Update changelog text. - Link: https://lore.kernel.org/linux-hardening/ZN02iLcZYgxHFrEN@work/ v1: - Link: https://lore.kernel.org/linux-hardening/ZIpm3pcs3iCP9UaR@work/ kernel/cgroup/cgroup.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index ccbbba06da5b..68e2d9812e3f 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -929,7 +929,7 @@ static void css_set_move_task(struct task_struct *task, #define CSS_SET_HASH_BITS 7 static DEFINE_HASHTABLE(css_set_table, CSS_SET_HASH_BITS); -static unsigned long css_set_hash(struct cgroup_subsys_state *css[]) +static unsigned long css_set_hash(struct cgroup_subsys_state **css) { unsigned long key = 0UL; struct cgroup_subsys *ss; @@ -1070,7 +1070,7 @@ static bool compare_css_sets(struct css_set *cset, */ static struct css_set *find_existing_css_set(struct css_set *old_cset, struct cgroup *cgrp, - struct cgroup_subsys_state *template[]) + struct cgroup_subsys_state **template) { struct cgroup_root *root = cgrp->root; struct cgroup_subsys *ss; -- 2.34.1