Re: [PATCH][next] cgroup: Avoid -Wstringop-overflow warnings

[Gustavo A. R. Silva]

Hi!

On 6/22/23 04:11, Steven Price wrote:
> On 15/06/2023 02:18, Gustavo A. R. Silva wrote:
> > 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=]
> >
> > These changes are based on commit d20d30ebb199 ("cgroup: Avoid compiler
> > warnings with no subsystems").
> >
> > Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
> > ---
> >   kernel/cgroup/cgroup.c | 6 ++++++
> >   1 file changed, 6 insertions(+)
> >
> > diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
> > index cd497b90e11a..1ee76e62eb98 100644
> > --- a/kernel/cgroup/cgroup.c
> > +++ b/kernel/cgroup/cgroup.c
> > @@ -1200,6 +1200,9 @@ static struct css_set *find_css_set(struct css_set *old_cset,
> >   	unsigned long key;
> >   	int ssid;
> >   
> > +	if (!CGROUP_HAS_SUBSYS_CONFIG)
> > +		return NULL;
> > +
> >   	lockdep_assert_held(&cgroup_mutex);
> >   
> >   	/* First see if we already have a cgroup group that matches
> > @@ -6045,6 +6048,9 @@ int __init cgroup_init(void)
> >   	struct cgroup_subsys *ss;
> >   	int ssid;
> >   
> > +	if (!CGROUP_HAS_SUBSYS_CONFIG)
> > +		return -EINVAL;
> > +
> >   	BUILD_BUG_ON(CGROUP_SUBSYS_COUNT > 16);
> >   	BUG_ON(cgroup_init_cftypes(NULL, cgroup_base_files));
> >   	BUG_ON(cgroup_init_cftypes(NULL, cgroup_psi_files));
>
> This change (which landed in linux-next) causes a boot failure on my
> (arm32) board because the cgroup filesystem isn't created which upsets
> systemd:
>
> [   11.474767] systemd[1]: Failed to mount tmpfs at /sys/fs/cgroup: No such file or directory
> [   11.489933] systemd[1]: Failed to mount cgroup at /sys/fs/cgroup/systemd: No such file or directory
> [!!!!!!] Failed to mount API filesystems.
>
> Reverting this commit on the head of linux-next gets the board working
> again.

Thanks for reporting this issue. I'll take a look.

--
Gustavo