From 4db430364722e719501672e7b3b76f2f3ca2b676 Mon Sep 17 00:00:00 2001 From: Jonathan Maple Date: Thu, 25 Sep 2025 17:02:49 -0400 Subject: [PATCH 1/3] bpf: Fix a segment issue when downgrading gso_size jira VULN-38755 cve CVE-2024-42281 commit-author Fred Li commit fa5ef655615a01533035c6139248c5b33aa27028 Linearize the skb when downgrading gso_size because it may trigger a BUG_ON() later when the skb is segmented as described in [1,2]. Fixes: 2be7e212d5419 ("bpf: add bpf_skb_adjust_room helper") Signed-off-by: Fred Li Signed-off-by: Daniel Borkmann Reviewed-by: Willem de Bruijn Acked-by: Daniel Borkmann Link: https://lore.kernel.org/all/20240626065555.35460-2-dracodingfly@gmail.com [1] Link: https://lore.kernel.org/all/668d5cf1ec330_1c18c32947@willemb.c.googlers.com.notmuch [2] Link: https://lore.kernel.org/bpf/20240719024653.77006-1-dracodingfly@gmail.com (cherry picked from commit fa5ef655615a01533035c6139248c5b33aa27028) Signed-off-by: Jonathan Maple --- net/core/filter.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/net/core/filter.c b/net/core/filter.c index 32fe3d2198de9..77d1877b39301 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -3481,13 +3481,20 @@ static int bpf_skb_net_grow(struct sk_buff *skb, u32 off, u32 len_diff, if (skb_is_gso(skb)) { struct skb_shared_info *shinfo = skb_shinfo(skb); - /* Due to header grow, MSS needs to be downgraded. */ - if (!(flags & BPF_F_ADJ_ROOM_FIXED_GSO)) - skb_decrease_gso_size(shinfo, len_diff); - /* Header must be checked, and gso_segs recomputed. */ shinfo->gso_type |= gso_type; shinfo->gso_segs = 0; + + /* Due to header growth, MSS needs to be downgraded. + * There is a BUG_ON() when segmenting the frag_list with + * head_frag true, so linearize the skb after downgrading + * the MSS. + */ + if (!(flags & BPF_F_ADJ_ROOM_FIXED_GSO)) { + skb_decrease_gso_size(shinfo, len_diff); + if (shinfo->frag_list) + return skb_linearize(skb); + } } return 0; From 1c6ca07dec21152703a34ef09692bf6e1337a6e1 Mon Sep 17 00:00:00 2001 From: Jonathan Maple Date: Fri, 26 Sep 2025 15:41:56 -0400 Subject: [PATCH 2/3] gso: fix udp gso fraglist segmentation after pull from frag_list jira VULN-45771 cve CVE-2024-49978 commit-author Willem de Bruijn commit a1e40ac5b5e9077fe1f7ae0eb88034db0f9ae1ab 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: 9fd1ff5d2ac7 ("udp: Support UDP fraglist GRO/GSO.") Signed-off-by: Willem de Bruijn Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20241001171752.107580-1-willemdebruijn.kernel@gmail.com Signed-off-by: Jakub Kicinski (cherry picked from commit a1e40ac5b5e9077fe1f7ae0eb88034db0f9ae1ab) Signed-off-by: Jonathan Maple --- net/ipv4/udp_offload.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c index 35e8250730a67..6475090333da0 100644 --- a/net/ipv4/udp_offload.c +++ b/net/ipv4/udp_offload.c @@ -273,8 +273,26 @@ struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb, __sum16 check; __be16 newlen; - if (skb_shinfo(gso_skb)->gso_type & SKB_GSO_FRAGLIST) - return __udp_gso_segment_list(gso_skb, features, is_ipv6); + 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); + } mss = skb_shinfo(gso_skb)->gso_size; if (gso_skb->len <= sizeof(*uh) + mss) From 5acbf59af0820d121659953d0c3e650cd330d097 Mon Sep 17 00:00:00 2001 From: Jonathan Maple Date: Fri, 26 Sep 2025 15:53:20 -0400 Subject: [PATCH 3/3] net: fix udp gso skb_segment after pull from frag_list jira VULN-71810 cve CVE-2025-38124 commit-author Shiming Cheng commit 3382a1ed7f778db841063f5d7e317ac55f9e7f72 Commit a1e40ac5b5e9 ("net: gso: fix udp gso fraglist segmentation after pull from frag_list") detected invalid geometry in frag_list skbs and redirects them from skb_segment_list to more robust skb_segment. But some packets with modified geometry can also hit bugs in that code. We don't know how many such cases exist. Addressing each one by one also requires touching the complex skb_segment code, which risks introducing bugs for other types of skbs. Instead, linearize all these packets that fail the basic invariants on gso fraglist skbs. That is more robust. If only part of the fraglist payload is pulled into head_skb, it will always cause exception when splitting skbs by skb_segment. For detailed call stack information, see below. 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 fraglist skbs, breaking these invariants. In extreme cases they pull one part of data into skb linear. For UDP, this causes three payloads with lengths of (11,11,10) bytes were pulled tail to become (12,10,10) bytes. The skbs no longer meets the above SKB_GSO_FRAGLIST conditions because payload was pulled into head_skb, it needs to be linearized before pass to regular skb_segment. skb_segment+0xcd0/0xd14 __udp_gso_segment+0x334/0x5f4 udp4_ufo_fragment+0x118/0x15c inet_gso_segment+0x164/0x338 skb_mac_gso_segment+0xc4/0x13c __skb_gso_segment+0xc4/0x124 validate_xmit_skb+0x9c/0x2c0 validate_xmit_skb_list+0x4c/0x80 sch_direct_xmit+0x70/0x404 __dev_queue_xmit+0x64c/0xe5c neigh_resolve_output+0x178/0x1c4 ip_finish_output2+0x37c/0x47c __ip_finish_output+0x194/0x240 ip_finish_output+0x20/0xf4 ip_output+0x100/0x1a0 NF_HOOK+0xc4/0x16c ip_forward+0x314/0x32c ip_rcv+0x90/0x118 __netif_receive_skb+0x74/0x124 process_backlog+0xe8/0x1a4 __napi_poll+0x5c/0x1f8 net_rx_action+0x154/0x314 handle_softirqs+0x154/0x4b8 [118.376811] [C201134] rxq0_pus: [name:bug&]kernel BUG at net/core/skbuff.c:4278! [118.376829] [C201134] rxq0_pus: [name:traps&]Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP [118.470774] [C201134] rxq0_pus: [name:mrdump&]Kernel Offset: 0x178cc00000 from 0xffffffc008000000 [118.470810] [C201134] rxq0_pus: [name:mrdump&]PHYS_OFFSET: 0x40000000 [118.470827] [C201134] rxq0_pus: [name:mrdump&]pstate: 60400005 (nZCv daif +PAN -UAO) [118.470848] [C201134] rxq0_pus: [name:mrdump&]pc : [0xffffffd79598aefc] skb_segment+0xcd0/0xd14 [118.470900] [C201134] rxq0_pus: [name:mrdump&]lr : [0xffffffd79598a5e8] skb_segment+0x3bc/0xd14 [118.470928] [C201134] rxq0_pus: [name:mrdump&]sp : ffffffc008013770 Fixes: a1e40ac5b5e9 ("gso: fix udp gso fraglist segmentation after pull from frag_list") Signed-off-by: Shiming Cheng Reviewed-by: Willem de Bruijn Signed-off-by: David S. Miller (cherry picked from commit 3382a1ed7f778db841063f5d7e317ac55f9e7f72) Signed-off-by: Jonathan Maple --- net/ipv4/udp_offload.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c index 6475090333da0..a786c22073f62 100644 --- a/net/ipv4/udp_offload.c +++ b/net/ipv4/udp_offload.c @@ -272,12 +272,17 @@ struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb, bool copy_dtor; __sum16 check; __be16 newlen; + int ret = 0; 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); + ret = __skb_linearize(gso_skb); + if (ret) + return ERR_PTR(ret); + /* 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);