6.6-stable review patch. If anyone has any objections, please let me know.
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From: Pu Lehui pulehui@huawei.com
[ Upstream commit 7dc211c1159d991db609bdf4b0fb9033c04adcbc ]
Syzkaller triggers an invalid memory access issue following fault injection in update_effective_progs. The issue can be described as follows:
__cgroup_bpf_detach update_effective_progs compute_effective_progs bpf_prog_array_alloc <-- fault inject purge_effective_progs /* change to dummy_bpf_prog */ array->items[index] = &dummy_bpf_prog.prog
---softirq start--- __do_softirq ... __cgroup_bpf_run_filter_skb __bpf_prog_run_save_cb bpf_prog_run stats = this_cpu_ptr(prog->stats) /* invalid memory access */ flags = u64_stats_update_begin_irqsave(&stats->syncp) ---softirq end---
static_branch_dec(&cgroup_bpf_enabled_key[atype])
The reason is that fault injection caused update_effective_progs to fail and then changed the original prog into dummy_bpf_prog.prog in purge_effective_progs. Then a softirq came, and accessing the members of dummy_bpf_prog.prog in the softirq triggers invalid mem access.
To fix it, skip updating stats when stats is NULL.
Fixes: 492ecee892c2 ("bpf: enable program stats") Signed-off-by: Pu Lehui pulehui@huawei.com Link: https://lore.kernel.org/r/20251115102343.2200727-1-pulehui@huaweicloud.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/filter.h | 12 +++++++----- kernel/bpf/syscall.c | 3 +++ 2 files changed, 10 insertions(+), 5 deletions(-)
diff --git a/include/linux/filter.h b/include/linux/filter.h index f9fb83be935d4..30fe140d48888 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -605,11 +605,13 @@ static __always_inline u32 __bpf_prog_run(const struct bpf_prog *prog, ret = dfunc(ctx, prog->insnsi, prog->bpf_func);
duration = sched_clock() - start; - stats = this_cpu_ptr(prog->stats); - flags = u64_stats_update_begin_irqsave(&stats->syncp); - u64_stats_inc(&stats->cnt); - u64_stats_add(&stats->nsecs, duration); - u64_stats_update_end_irqrestore(&stats->syncp, flags); + if (likely(prog->stats)) { + stats = this_cpu_ptr(prog->stats); + flags = u64_stats_update_begin_irqsave(&stats->syncp); + u64_stats_inc(&stats->cnt); + u64_stats_add(&stats->nsecs, duration); + u64_stats_update_end_irqrestore(&stats->syncp, flags); + } } else { ret = dfunc(ctx, prog->insnsi, prog->bpf_func); } diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 98f3f206d112e..63cf5a221081b 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -2224,6 +2224,9 @@ void notrace bpf_prog_inc_misses_counter(struct bpf_prog *prog) struct bpf_prog_stats *stats; unsigned int flags;
+ if (unlikely(!prog->stats)) + return; + stats = this_cpu_ptr(prog->stats); flags = u64_stats_update_begin_irqsave(&stats->syncp); u64_stats_inc(&stats->misses);