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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Hou Tao <houtao1@huawei.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Martin KaFai Lau <martin.lau@kernel.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 6.0 256/862] bpf: Use this_cpu_{inc|dec|inc_return} for bpf_task_storage_busy
Date:   Wed, 19 Oct 2022 10:25:43 +0200
Message-Id: <20221019083301.365324583@linuxfoundation.org>
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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;
 	}
-- 
2.35.1