cgroup: Avoid -Wstringop-overflow warnings
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 <gustavoars@kernel.org> Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: Tejun Heo <tj@kernel.org>
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