linux-kernel - [PATCH AUTOSEL 5.15 6/7] bpf: fix possible endless loop in BPF map iteration

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Message-Id: <20250429235339.538269-6-sashal@kernel.org>
Date: Tue, 29 Apr 2025 19:53:37 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Brandon Kammerdiener <brandon.kammerdiener@...el.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Hou Tao <houtao1@...wei.com>,
	Sasha Levin <sashal@...nel.org>,
	daniel@...earbox.net,
	andrii@...nel.org,
	bpf@...r.kernel.org
Subject: [PATCH AUTOSEL 5.15 6/7] bpf: fix possible endless loop in BPF map iteration

From: Brandon Kammerdiener <brandon.kammerdiener@...el.com>

[ Upstream commit 75673fda0c557ae26078177dd14d4857afbf128d ]

The _safe variant used here gets the next element before running the callback,
avoiding the endless loop condition.

Signed-off-by: Brandon Kammerdiener <brandon.kammerdiener@...el.com>
Link: https://lore.kernel.org/r/20250424153246.141677-2-brandon.kammerdiener@intel.com
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
Acked-by: Hou Tao <houtao1@...wei.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 kernel/bpf/hashtab.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index d08fe64e0e453..24258c54057d4 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -2102,7 +2102,7 @@ static int bpf_for_each_hash_elem(struct bpf_map *map, void *callback_fn,
 		b = &htab->buckets[i];
 		rcu_read_lock();
 		head = &b->head;
-		hlist_nulls_for_each_entry_rcu(elem, n, head, hash_node) {
+		hlist_nulls_for_each_entry_safe(elem, n, head, hash_node) {
 			key = elem->key;
 			if (is_percpu) {
 				/* current cpu value for percpu map */
-- 
2.39.5