On Thu 15-06-23 07:32:26, Haifeng Xu wrote: > If mem_cgroup_init() fails to allocate mem_cgroup_tree_per_node, we > should not try to initilaize it. Add check for this case to avoid > potential NULL pointer dereference. Technically yes and it seems that all users of soft_limit_tree.rb_tree_per_node correctly check for NULL so this would be graceful failure handling. At least superficially because the feature itself would be semi-broken when used. But more practically this is a 24B allocation and if we fail to allocate that early during the boot we are screwed anyway. Would such a system have any chance to boot all the way to userspace? Woul any userspace actually work? Is this patch motivated by a code reading or is there any actual practical upside of handling the error here? > Signed-off-by: Haifeng Xu <haifeng.xu@xxxxxxxxxx> > --- > mm/memcontrol.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index c73c5fb33f65..7ebf64e48b25 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -7422,6 +7422,8 @@ static int __init mem_cgroup_init(void) > struct mem_cgroup_tree_per_node *rtpn; > > rtpn = kzalloc_node(sizeof(*rtpn), GFP_KERNEL, node); > + if (!rtpn) > + continue; > > rtpn->rb_root = RB_ROOT; > rtpn->rb_rightmost = NULL; > -- > 2.25.1 -- Michal Hocko SUSE Labs
