linux-kernel - [PATCH 5.10 038/105] bpf, sockmap: Do not ignore orig

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Date:   Mon,  7 Mar 2022 10:18:41 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, syzbot <syzkaller@...glegroups.com>,
        Eric Dumazet <edumazet@...gle.com>,
        John Fastabend <john.fastabend@...il.com>,
        Jakub Sitnicki <jakub@...udflare.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH 5.10 038/105] bpf, sockmap: Do not ignore orig_len parameter

From: Eric Dumazet <edumazet@...gle.com>

commit 60ce37b03917e593d8e5d8bcc7ec820773daf81d upstream.

Currently, sk_psock_verdict_recv() returns skb->len

This is problematic because tcp_read_sock() might have
passed orig_len < skb->len, due to the presence of TCP urgent data.

This causes an infinite loop from tcp_read_sock()

Followup patch will make tcp_read_sock() more robust vs bad actors.

Fixes: ef5659280eb1 ("bpf, sockmap: Allow skipping sk_skb parser program")
Reported-by: syzbot <syzkaller@...glegroups.com>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Acked-by: John Fastabend <john.fastabend@...il.com>
Acked-by: Jakub Sitnicki <jakub@...udflare.com>
Tested-by: Jakub Sitnicki <jakub@...udflare.com>
Acked-by: Daniel Borkmann <daniel@...earbox.net>
Link: https://lore.kernel.org/r/20220302161723.3910001-1-eric.dumazet@gmail.com
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/core/skmsg.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/core/skmsg.c
+++ b/net/core/skmsg.c
@@ -943,7 +943,7 @@ static int sk_psock_verdict_recv(read_de
 	struct sk_psock *psock;
 	struct bpf_prog *prog;
 	int ret = __SK_DROP;
-	int len = skb->len;
+	int len = orig_len;
 
 	/* clone here so sk_eat_skb() in tcp_read_sock does not drop our data */
 	skb = skb_clone(skb, GFP_ATOMIC);