netdev - [PATCH bpf] sock_map: add a cond_resched() in sock_hash

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Message-ID: <20240906154449.3742932-1-edumazet@google.com>
Date: Fri,  6 Sep 2024 15:44:49 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Daniel Borkmann <daniel@...earbox.net>, 
	Alexei Starovoitov <ast@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>
Cc: Andrii Nakryiko <andrii@...nel.org>, netdev@...r.kernel.org, bpf@...r.kernel.org, 
	eric.dumazet@...il.com, Eric Dumazet <edumazet@...gle.com>, 
	syzbot <syzkaller@...glegroups.com>, John Fastabend <john.fastabend@...il.com>, 
	Jakub Sitnicki <jakub@...udflare.com>
Subject: [PATCH bpf] sock_map: add a cond_resched() in sock_hash_free()

Several syzbot soft lockup reports all have in common sock_hash_free()

If a map with a large number of buckets is destroyed, we need to yield
the cpu when needed.

Fixes: 75e68e5bf2c7 ("bpf, sockhash: Synchronize delete from bucket list on map free")
Reported-by: syzbot <syzkaller@...glegroups.com>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: John Fastabend <john.fastabend@...il.com>
Cc: Jakub Sitnicki <jakub@...udflare.com>
---
 net/core/sock_map.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index d3dbb92153f2fe7f1ddc8e35b495533fbf60a8cb..724b6856fcc3e9fd51673d31927cfd52d5d7d0aa 100644
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -1183,6 +1183,7 @@ static void sock_hash_free(struct bpf_map *map)
 			sock_put(elem->sk);
 			sock_hash_free_elem(htab, elem);
 		}
+		cond_resched();
 	}
 
 	/* wait for psock readers accessing its map link */
-- 
2.46.0.469.g59c65b2a67-goog