Commit 9d4f8f2e authored by Willem de Bruijn's avatar Willem de Bruijn Committed by Liu Jian
Browse files

gso: fix udp gso fraglist segmentation after pull from frag_list 

stable inclusion
from stable-v6.6.55
commit af3122f5fdc0d00581d6e598a668df6bf54c9daa
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAYRAJ
CVE: CVE-2024-49978

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=af3122f5fdc0d00581d6e598a668df6bf54c9daa

-------------------------------------------------

commit a1e40ac5b5e9077fe1f7ae0eb88034db0f9ae1ab upstream.

Detect gso fraglist skbs with corrupted geometry (see below) and
pass these to skb_segment instead of skb_segment_list, as the first
can segment them correctly.

Valid SKB_GSO_FRAGLIST skbs
- consist of two or more segments
- the head_skb holds the protocol headers plus first gso_size
- one or more frag_list skbs hold exactly one segment
- all but the last must be gso_size

Optional datapath hooks such as NAT and BPF (bpf_skb_pull_data) can
modify these skbs, breaking these invariants.

In extreme cases they pull all data into skb linear. For UDP, this
causes a NULL ptr deref in __udpv4_gso_segment_list_csum at
udp_hdr(seg->next)->dest.

Detect invalid geometry due to pull, by checking head_skb size.
Don't just drop, as this may blackhole a destination. Convert to be
able to pass to regular skb_segment.

Link: https://lore.kernel.org/netdev/20240428142913.18666-1-shiming.cheng@mediatek.com/


Fixes: 9fd1ff5d ("udp: Support UDP fraglist GRO/GSO.")
Signed-off-by: default avatarWillem de Bruijn <willemb@google.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20241001171752.107580-1-willemdebruijn.kernel@gmail.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarLiu Jian <liujian56@huawei.com>
parent 2ff12244

net/ipv4/udp_offload.c

+20 −2
Original line number Diff line number Diff line
@@ -290,9 +290,27 @@ struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb, 
		return NULL;

	}



	if (skb_shinfo(gso_skb)->gso_type & SKB_GSO_FRAGLIST)

	if (skb_shinfo(gso_skb)->gso_type & SKB_GSO_FRAGLIST) {

		 /* Detect modified geometry and pass those to skb_segment. */

		if (skb_pagelen(gso_skb) - sizeof(*uh) == skb_shinfo(gso_skb)->gso_size)

			return __udp_gso_segment_list(gso_skb, features, is_ipv6);



		 /* Setup csum, as fraglist skips this in udp4_gro_receive. */

		gso_skb->csum_start = skb_transport_header(gso_skb) - gso_skb->head;

		gso_skb->csum_offset = offsetof(struct udphdr, check);

		gso_skb->ip_summed = CHECKSUM_PARTIAL;



		uh = udp_hdr(gso_skb);

		if (is_ipv6)

			uh->check = ~udp_v6_check(gso_skb->len,

						  &ipv6_hdr(gso_skb)->saddr,

						  &ipv6_hdr(gso_skb)->daddr, 0);

		else

			uh->check = ~udp_v4_check(gso_skb->len,

						  ip_hdr(gso_skb)->saddr,

						  ip_hdr(gso_skb)->daddr, 0);

	}



	skb_pull(gso_skb, sizeof(*uh));



	/* clear destructor to avoid skb_segment assigning it to tail */