From d8c4f23ecdaf59350e686b786860a41a2e4d4dda Mon Sep 17 00:00:00 2001 From: Stas Sergeev Date: Tue, 29 Aug 2023 21:44:06 +0500 Subject: tap: fix uses of l3_len in tap4_handler() l3_len was calculated from the ethernet frame size, and it was assumed to be equal to the length stored in an IP packet. But if the ethernet frame is padded, then l3_len calculated that way can only be used as a bound check to validate the length stored in an IP header. It should not be used for calculating the l4_len. This patch makes sure the small padded ethernet frames are properly processed, by trusting the length stored in an IP header. Link: https://bugs.passt.top/show_bug.cgi?id=73 Signed-off-by: Stas Sergeev Signed-off-by: Stefano Brivio --- tap.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/tap.c b/tap.c index ee79be0..8d7859c 100644 --- a/tap.c +++ b/tap.c @@ -615,7 +615,7 @@ resume: continue; hlen = iph->ihl * 4UL; - if (hlen < sizeof(*iph) || htons(iph->tot_len) != l3_len || + if (hlen < sizeof(*iph) || htons(iph->tot_len) > l3_len || hlen > l3_len) continue; @@ -623,7 +623,7 @@ resume: if (tap4_is_fragment(iph, now)) continue; - l4_len = l3_len - hlen; + l4_len = htons(iph->tot_len) - hlen; if (iph->saddr && c->ip4.addr_seen.s_addr != iph->saddr) c->ip4.addr_seen.s_addr = iph->saddr; -- cgit v1.2.3