Re: [PATCH net-next 06/10] cipso_ipv4: use iph_set_totlen in skbuff_setattr
From: Paul Moore <paul@paul-moore.com>
Date: 2023-01-14 15:39:18
Also in:
netdev, selinux
On Fri, Jan 13, 2023 at 10:31 PM Xin Long [off-list ref] wrote:
It may process IPv4 TCP GSO packets in cipso_v4_skbuff_setattr(), so the iph->tot_len update should use iph_set_totlen(). Note that for these non GSO packets, the new iph tot_len with extra iph option len added may become greater than 65535, the old process will cast it and set iph->tot_len to it, which is a bug. In theory, iph options shouldn't be added for these big packets in here, a fix may be needed here in the future. For now this patch is only to set iph->tot_len to 0 when it happens.
I'm not entirely clear on the paragraph above, but we do need to be able to set/modify the IP options in cipso_v4_skbuff_setattr() in order to support CIPSO labeling. I'm open to better and/or alternative solutions compared to what we are doing now, but I can't support a change that is a bug waiting to bite us. My apologies if I'm interpreting your comments incorrectly and that isn't the case here.
quoted hunk
Signed-off-by: Xin Long <lucien.xin@gmail.com> --- net/ipv4/cipso_ipv4.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/net/ipv4/cipso_ipv4.c b/net/ipv4/cipso_ipv4.c index 6cd3b6c559f0..79ae7204e8ed 100644 --- a/net/ipv4/cipso_ipv4.c +++ b/net/ipv4/cipso_ipv4.c@@ -2222,7 +2222,7 @@ int cipso_v4_skbuff_setattr(struct sk_buff *skb, memset((char *)(iph + 1) + buf_len, 0, opt_len - buf_len); if (len_delta != 0) { iph->ihl = 5 + (opt_len >> 2); - iph->tot_len = htons(skb->len); + iph_set_totlen(iph, skb->len); } ip_send_check(iph); --2.31.1
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