From 8817005efbdfdf5d4e4814cb5dc52b53d12917d7 Mon Sep 17 00:00:00 2001 From: Qing Ming Date: Sat, 16 May 2026 15:08:49 +0800 Subject: cgroup/rstat: validate cpu before css_rstat_cpu() access css_rstat_updated() is exposed as a BPF kfunc and accepts a caller-provided cpu argument. The function uses cpu for per-cpu rstat lookups without checking whether it refers to a valid possible CPU. A BPF iter/cgroup program with CAP_BPF and CAP_PERFMON can pass an invalid cpu value. On an unfixed UBSCAN_BOUNDS test kernel, cpu == 0x7fffffff triggers: UBSAN: array-index-out-of-bounds in kernel/cgroup/rstat.c:31:9 index 2147483647 is out of range for type 'long unsigned int [64]' Call Trace: css_rstat_updated bpf_iter_run_prog cgroup_iter_seq_show bpf_seq_read Add cpu validation to the BPF-facing css_rstat_updated() kfunc and move the common implementation to __css_rstat_updated() for in-kernel callers. Fixes: a319185be9f5 ("cgroup: bpf: enable bpf programs to integrate with rstat") Signed-off-by: Qing Ming Signed-off-by: Tejun Heo --- mm/memcontrol.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'mm') diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 051b82ebf371..c7e60f26013c 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -579,7 +579,7 @@ static inline void memcg_rstat_updated(struct mem_cgroup *memcg, int val, if (!val) return; - css_rstat_updated(&memcg->css, cpu); + __css_rstat_updated(&memcg->css, cpu); statc_pcpu = memcg->vmstats_percpu; for (; statc_pcpu; statc_pcpu = statc->parent_pcpu) { statc = this_cpu_ptr(statc_pcpu); @@ -2608,7 +2608,7 @@ static inline void account_slab_nmi_safe(struct mem_cgroup *memcg, struct mem_cgroup_per_node *pn = memcg->nodeinfo[pgdat->node_id]; /* preemption is disabled in_nmi(). */ - css_rstat_updated(&memcg->css, smp_processor_id()); + __css_rstat_updated(&memcg->css, smp_processor_id()); if (idx == NR_SLAB_RECLAIMABLE_B) atomic_add(nr, &pn->slab_reclaimable); else @@ -2832,7 +2832,7 @@ static inline void account_kmem_nmi_safe(struct mem_cgroup *memcg, int val) mod_memcg_state(memcg, MEMCG_KMEM, val); } else { /* preemption is disabled in_nmi(). */ - css_rstat_updated(&memcg->css, smp_processor_id()); + __css_rstat_updated(&memcg->css, smp_processor_id()); atomic_add(val, &memcg->kmem_stat); } } -- cgit v1.2.3