Commit Message
Greg KH
Oct. 22, 2022, 7:21 a.m. UTC
From: Hou Tao <houtao1@huawei.com> [ Upstream commit 197827a05e13808c60f52632e9887eede63f1c16 ] Now migrate_disable() does not disable preemption and under some architectures (e.g. arm64) __this_cpu_{inc|dec|inc_return} are neither preemption-safe nor IRQ-safe, so for fully preemptible kernel concurrent lookups or updates on the same task local storage and on the same CPU may make bpf_task_storage_busy be imbalanced, and bpf_task_storage_trylock() on the specific cpu will always fail. Fixing it by using this_cpu_{inc|dec|inc_return} when manipulating bpf_task_storage_busy. Fixes: bc235cdb423a ("bpf: Prevent deadlock from recursive bpf_task_storage_[get|delete]") Signed-off-by: Hou Tao <houtao1@huawei.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/r/20220901061938.3789460-2-houtao@huaweicloud.com Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> --- kernel/bpf/bpf_local_storage.c | 4 ++-- kernel/bpf/bpf_task_storage.c | 8 ++++---- 2 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c index 8ce40fd869f6..d13ffb00e981 100644 --- a/kernel/bpf/bpf_local_storage.c +++ b/kernel/bpf/bpf_local_storage.c @@ -555,11 +555,11 @@ void bpf_local_storage_map_free(struct bpf_local_storage_map *smap, struct bpf_local_storage_elem, map_node))) { if (busy_counter) { migrate_disable(); - __this_cpu_inc(*busy_counter); + this_cpu_inc(*busy_counter); } bpf_selem_unlink(selem, false); if (busy_counter) { - __this_cpu_dec(*busy_counter); + this_cpu_dec(*busy_counter); migrate_enable(); } cond_resched_rcu(); diff --git a/kernel/bpf/bpf_task_storage.c b/kernel/bpf/bpf_task_storage.c index e9014dc62682..6f290623347e 100644 --- a/kernel/bpf/bpf_task_storage.c +++ b/kernel/bpf/bpf_task_storage.c @@ -26,20 +26,20 @@ static DEFINE_PER_CPU(int, bpf_task_storage_busy); static void bpf_task_storage_lock(void) { migrate_disable(); - __this_cpu_inc(bpf_task_storage_busy); + this_cpu_inc(bpf_task_storage_busy); } static void bpf_task_storage_unlock(void) { - __this_cpu_dec(bpf_task_storage_busy); + this_cpu_dec(bpf_task_storage_busy); migrate_enable(); } static bool bpf_task_storage_trylock(void) { migrate_disable(); - if (unlikely(__this_cpu_inc_return(bpf_task_storage_busy) != 1)) { - __this_cpu_dec(bpf_task_storage_busy); + if (unlikely(this_cpu_inc_return(bpf_task_storage_busy) != 1)) { + this_cpu_dec(bpf_task_storage_busy); migrate_enable(); return false; }