kernel/linux.git/include/linux/skbuff.h, branch v6.1.168

net: add skb_header_pointer_careful() helper

2026-03-25T10:03:18+00:00

[ Upstream commit 13e00fdc9236bd4d0bff4109d2983171fbcb74c4 ] This variant of skb_header_pointer() should be used in contexts where @offset argument is user-controlled and could be negative. Negative offsets are supported, as long as the zone starts between skb->head and skb->data. Signed-off-by: Eric Dumazet Link: https://patch.msgid.link/20260128141539.3404400-2-edumazet@google.com Signed-off-by: Jakub Kicinski [ Adjust context ] Signed-off-by: Bin Lan Signed-off-by: Greg Kroah-Hartman

net: Add skb_dstref_steal and skb_dstref_restore

2026-03-04T12:19:45+00:00

[ Upstream commit c3f0c02997c7f8489fec259e28e0e04e9811edac ] Going forward skb_dst_set will assert that skb dst_entry is empty during skb_dst_set to prevent potential leaks. There are few places that still manually manage dst_entry not using the helpers. Convert them to the following new helpers: - skb_dstref_steal that resets dst_entry and returns previous dst_entry value - skb_dstref_restore that restores dst_entry previously reset via skb_dstref_steal Signed-off-by: Stanislav Fomichev Link: https://patch.msgid.link/20250818154032.3173645-2-sdf@fomichev.me Signed-off-by: Jakub Kicinski Stable-dep-of: 81b84de32bb2 ("xfrm: fix ip_rt_bug race in icmp_route_lookup reverse path") Signed-off-by: Sasha Levin

netmem: fix skb_frag_address_safe with unreadable skbs

2025-08-28T14:25:57+00:00

[ Upstream commit 4672aec56d2e8edabcb74c3e2320301d106a377e ] skb_frag_address_safe() needs a check that the skb_frag_page exists check similar to skb_frag_address(). Cc: ap420073@gmail.com Signed-off-by: Mina Almasry Acked-by: Stanislav Fomichev Link: https://patch.msgid.link/20250619175239.3039329-1-almasrymina@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

ipv6: reject malicious packets in ipv6_gso_segment()

2025-08-15T10:05:10+00:00

[ Upstream commit d45cf1e7d7180256e17c9ce88e32e8061a7887fe ] syzbot was able to craft a packet with very long IPv6 extension headers leading to an overflow of skb->transport_header. This 16bit field has a limited range. Add skb_reset_transport_header_careful() helper and use it from ipv6_gso_segment() WARNING: CPU: 0 PID: 5871 at ./include/linux/skbuff.h:3032 skb_reset_transport_header include/linux/skbuff.h:3032 [inline] WARNING: CPU: 0 PID: 5871 at ./include/linux/skbuff.h:3032 ipv6_gso_segment+0x15e2/0x21e0 net/ipv6/ip6_offload.c:151 Modules linked in: CPU: 0 UID: 0 PID: 5871 Comm: syz-executor211 Not tainted 6.16.0-rc6-syzkaller-g7abc678e3084 #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 RIP: 0010:skb_reset_transport_header include/linux/skbuff.h:3032 [inline] RIP: 0010:ipv6_gso_segment+0x15e2/0x21e0 net/ipv6/ip6_offload.c:151 Call Trace: skb_mac_gso_segment+0x31c/0x640 net/core/gso.c:53 nsh_gso_segment+0x54a/0xe10 net/nsh/nsh.c:110 skb_mac_gso_segment+0x31c/0x640 net/core/gso.c:53 __skb_gso_segment+0x342/0x510 net/core/gso.c:124 skb_gso_segment include/net/gso.h:83 [inline] validate_xmit_skb+0x857/0x11b0 net/core/dev.c:3950 validate_xmit_skb_list+0x84/0x120 net/core/dev.c:4000 sch_direct_xmit+0xd3/0x4b0 net/sched/sch_generic.c:329 __dev_xmit_skb net/core/dev.c:4102 [inline] __dev_queue_xmit+0x17b6/0x3a70 net/core/dev.c:4679 Fixes: d1da932ed4ec ("ipv6: Separate ipv6 offload support") Reported-by: syzbot+af43e647fd835acc02df@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/688a1a05.050a0220.5d226.0008.GAE@google.com/T/#u Signed-off-by: Eric Dumazet Reviewed-by: Dawid Osuchowski Reviewed-by: Willem de Bruijn Link: https://patch.msgid.link/20250730131738.3385939-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

net: add pskb_may_pull_reason() helper

2024-06-12T09:03:32+00:00

[ Upstream commit 1fb2d41501f38192d8a19da585cd441cf8845697 ] pskb_may_pull() can fail for two different reasons. Provide pskb_may_pull_reason() helper to distinguish between these reasons. It returns: SKB_NOT_DROPPED_YET : Success SKB_DROP_REASON_PKT_TOO_SMALL : packet too small SKB_DROP_REASON_NOMEM : skb->head could not be resized Signed-off-by: Eric Dumazet Reviewed-by: David Ahern Signed-off-by: Jakub Kicinski Stable-dep-of: 8bd67ebb50c0 ("net: bridge: xmit: make sure we have at least eth header len bytes") Signed-off-by: Sasha Levin

xfrm: Preserve vlan tags for transport mode software GRO

2024-05-17T09:56:10+00:00

[ Upstream commit 58fbfecab965014b6e3cc956a76b4a96265a1add ] The software GRO path for esp transport mode uses skb_mac_header_rebuild prior to re-injecting the packet via the xfrm_napi_dev. This only copies skb->mac_len bytes of header which may not be sufficient if the packet contains 802.1Q tags or other VLAN tags. Worse copying only the initial header will leave a packet marked as being VLAN tagged but without the corresponding tag leading to mangling when it is later untagged. The VLAN tags are important when receiving the decrypted esp transport mode packet after GRO processing to ensure it is received on the correct interface. Therefore record the full mac header length in xfrm*_transport_input for later use in corresponding xfrm*_transport_finish to copy the entire mac header when rebuilding the mac header for GRO. The skb->data pointer is left pointing skb->mac_header bytes after the start of the mac header as is expected by the network stack and network and transport header offsets reset to this location. Fixes: 7785bba299a8 ("esp: Add a software GRO codepath") Signed-off-by: Paul Davey Signed-off-by: Steffen Klassert Signed-off-by: Sasha Levin

net: mpls: error out if inner headers are not set

2024-04-13T11:05:27+00:00

commit 025f8ad20f2e3264d11683aa9cbbf0083eefbdcd upstream. mpls_gso_segment() assumes skb_inner_network_header() returns a valid result: mpls_hlen = skb_inner_network_header(skb) - skb_network_header(skb); if (unlikely(!mpls_hlen || mpls_hlen % MPLS_HLEN)) goto out; if (unlikely(!pskb_may_pull(skb, mpls_hlen))) With syzbot reproducer, skb_inner_network_header() yields 0, skb_network_header() returns 108, so this will "pskb_may_pull(skb, -108)))" which triggers a newly added DEBUG_NET_WARN_ON_ONCE() check: ------------[ cut here ]------------ WARNING: CPU: 0 PID: 5068 at include/linux/skbuff.h:2723 pskb_may_pull_reason include/linux/skbuff.h:2723 [inline] WARNING: CPU: 0 PID: 5068 at include/linux/skbuff.h:2723 pskb_may_pull include/linux/skbuff.h:2739 [inline] WARNING: CPU: 0 PID: 5068 at include/linux/skbuff.h:2723 mpls_gso_segment+0x773/0xaa0 net/mpls/mpls_gso.c:34 [..] skb_mac_gso_segment+0x383/0x740 net/core/gso.c:53 nsh_gso_segment+0x40a/0xad0 net/nsh/nsh.c:108 skb_mac_gso_segment+0x383/0x740 net/core/gso.c:53 __skb_gso_segment+0x324/0x4c0 net/core/gso.c:124 skb_gso_segment include/net/gso.h:83 [inline] [..] sch_direct_xmit+0x11a/0x5f0 net/sched/sch_generic.c:327 [..] packet_sendmsg+0x46a9/0x6130 net/packet/af_packet.c:3113 [..] First iteration of this patch made mpls_hlen signed and changed test to error out to "mpls_hlen <= 0 || ..". Eric Dumazet said: > I was thinking about adding a debug check in skb_inner_network_header() > if inner_network_header is zero (that would mean it is not 'set' yet), > but this would trigger even after your patch. So add new skb_inner_network_header_was_set() helper and use that. The syzbot reproducer injects data via packet socket. The skb that gets allocated and passed down the stack has ->protocol set to NSH (0x894f) and gso_type set to SKB_GSO_UDP | SKB_GSO_DODGY. This gets passed to skb_mac_gso_segment(), which sees NSH as ptype to find a callback for. nsh_gso_segment() retrieves next type: proto = tun_p_to_eth_p(nsh_hdr(skb)->np); ... which is MPLS (TUN_P_MPLS_UC). It updates skb->protocol and then calls mpls_gso_segment(). Inner offsets are all 0, so mpls_gso_segment() ends up with a negative header size. In case more callers rely on silent handling of such large may_pull values we could also 'legalize' this behaviour, either replacing the debug check with (len > INT_MAX) test or removing it and instead adding a comment before existing if (unlikely(len > skb->len)) return SKB_DROP_REASON_PKT_TOO_SMALL; test in pskb_may_pull_reason(), saying that this check also implicitly takes care of callers that miscompute header sizes. Cc: Simon Horman Fixes: 219eee9c0d16 ("net: skbuff: add overflow debug check to pull/push helpers") Reported-by: syzbot+99d15fcdb0132a1e1a82@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/00000000000043b1310611e388aa@google.com/raw Signed-off-by: Florian Westphal Link: https://lore.kernel.org/r/20240222140321.14080-1-fw@strlen.de Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

net: skbuff: add overflow debug check to pull/push helpers

2024-04-13T11:04:56+00:00

[ Upstream commit 219eee9c0d16f1b754a8b85275854ab17df0850a ] syzbot managed to trigger following splat: BUG: KASAN: use-after-free in __skb_flow_dissect+0x4a3b/0x5e50 Read of size 1 at addr ffff888208a4000e by task a.out/2313 [..] __skb_flow_dissect+0x4a3b/0x5e50 __skb_get_hash+0xb4/0x400 ip_tunnel_xmit+0x77e/0x26f0 ipip_tunnel_xmit+0x298/0x410 .. Analysis shows that the skb has a valid ->head, but bogus ->data pointer. skb->data gets its bogus value via the neigh layer, which does: 1556 __skb_pull(skb, skb_network_offset(skb)); ... and the skb was already dodgy at this point: skb_network_offset(skb) returns a negative value due to an earlier overflow of skb->network_header (u16). __skb_pull thus "adjusts" skb->data by a huge offset, pointing outside skb->head area. Allow debug builds to splat when we try to pull/push more than INT_MAX bytes. After this, the syzkaller reproducer yields a more precise splat before the flow dissector attempts to read off skb->data memory: WARNING: CPU: 5 PID: 2313 at include/linux/skbuff.h:2653 neigh_connected_output+0x28e/0x400 ip_finish_output2+0xb25/0xed0 iptunnel_xmit+0x4ff/0x870 ipgre_xmit+0x78e/0xbb0 Signed-off-by: Florian Westphal Reviewed-by: Simon Horman Link: https://lore.kernel.org/r/20240216113700.23013-1-fw@strlen.de Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin

inet: inet_defrag: prevent sk release while still in use

2024-04-10T14:28:23+00:00

[ Upstream commit 18685451fc4e546fc0e718580d32df3c0e5c8272 ] ip_local_out() and other functions can pass skb->sk as function argument. If the skb is a fragment and reassembly happens before such function call returns, the sk must not be released. This affects skb fragments reassembled via netfilter or similar modules, e.g. openvswitch or ct_act.c, when run as part of tx pipeline. Eric Dumazet made an initial analysis of this bug. Quoting Eric: Calling ip_defrag() in output path is also implying skb_orphan(), which is buggy because output path relies on sk not disappearing. A relevant old patch about the issue was : 8282f27449bf ("inet: frag: Always orphan skbs inside ip_defrag()") [..] net/ipv4/ip_output.c depends on skb->sk being set, and probably to an inet socket, not an arbitrary one. If we orphan the packet in ipvlan, then downstream things like FQ packet scheduler will not work properly. We need to change ip_defrag() to only use skb_orphan() when really needed, ie whenever frag_list is going to be used. Eric suggested to stash sk in fragment queue and made an initial patch. However there is a problem with this: If skb is refragmented again right after, ip_do_fragment() will copy head->sk to the new fragments, and sets up destructor to sock_wfree. IOW, we have no choice but to fix up sk_wmem accouting to reflect the fully reassembled skb, else wmem will underflow. This change moves the orphan down into the core, to last possible moment. As ip_defrag_offset is aliased with sk_buff->sk member, we must move the offset into the FRAG_CB, else skb->sk gets clobbered. This allows to delay the orphaning long enough to learn if the skb has to be queued or if the skb is completing the reasm queue. In the former case, things work as before, skb is orphaned. This is safe because skb gets queued/stolen and won't continue past reasm engine. In the latter case, we will steal the skb->sk reference, reattach it to the head skb, and fix up wmem accouting when inet_frag inflates truesize. Fixes: 7026b1ddb6b8 ("netfilter: Pass socket pointer down through okfn().") Diagnosed-by: Eric Dumazet Reported-by: xingwei lee Reported-by: yue sun Reported-by: syzbot+e5167d7144a62715044c@syzkaller.appspotmail.com Signed-off-by: Florian Westphal Reviewed-by: Eric Dumazet Link: https://lore.kernel.org/r/20240326101845.30836-1-fw@strlen.de Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin

netfilter: bridge: replace physindev with physinif in nf_bridge_info

2024-01-25T23:27:51+00:00

[ Upstream commit 9874808878d9eed407e3977fd11fee49de1e1d86 ] An skb can be added to a neigh->arp_queue while waiting for an arp reply. Where original skb's skb->dev can be different to neigh's neigh->dev. For instance in case of bridging dnated skb from one veth to another, the skb would be added to a neigh->arp_queue of the bridge. As skb->dev can be reset back to nf_bridge->physindev and used, and as there is no explicit mechanism that prevents this physindev from been freed under us (for instance neigh_flush_dev doesn't cleanup skbs from different device's neigh queue) we can crash on e.g. this stack: arp_process neigh_update skb = __skb_dequeue(&neigh->arp_queue) neigh_resolve_output(..., skb) ... br_nf_dev_xmit br_nf_pre_routing_finish_bridge_slow skb->dev = nf_bridge->physindev br_handle_frame_finish Let's use plain ifindex instead of net_device link. To peek into the original net_device we will use dev_get_by_index_rcu(). Thus either we get device and are safe to use it or we don't get it and drop skb. Fixes: c4e70a87d975 ("netfilter: bridge: rename br_netfilter.c to br_netfilter_hooks.c") Suggested-by: Florian Westphal Signed-off-by: Pavel Tikhomirov Signed-off-by: Pablo Neira Ayuso Signed-off-by: Sasha Levin