erspan: make sure erspan_base_hdr is present in skb->head

Summary

In the Linux kernel, the following vulnerability has been resolved: erspan: make sure erspan_base_hdr is present in skb->head syzbot reported a problem in ip6erspan_rcv() [1] Issue is that ip6erspan_rcv() (and erspan_rcv()) no longer make sure erspan_base_hdr is present in skb linear part (skb->head) before getting @ver field from it. Add the missing pskb_may_pull() calls. v2: Reload iph pointer in erspan_rcv() after pskb_may_pull() because skb->head might have changed. [1] BUG: KMSAN: uninit-value in pskb_may_pull_reason include/linux/skbuff.h:2742 [inline] BUG: KMSAN: uninit-value in pskb_may_pull include/linux/skbuff.h:2756 [inline] BUG: KMSAN: uninit-value in ip6erspan_rcv net/ipv6/ip6_gre.c:541 [inline] BUG: KMSAN: uninit-value in gre_rcv+0x11f8/0x1930 net/ipv6/ip6_gre.c:610 pskb_may_pull_reason include/linux/skbuff.h:2742 [inline] pskb_may_pull include/linux/skbuff.h:2756 [inline] ip6erspan_rcv net/ipv6/ip6_gre.c:541 [inline] gre_rcv+0x11f8/0x1930 net/ipv6/ip6_gre.c:610 ip6_protocol_deliver_rcu+0x1d4c/0x2ca0 net/ipv6/ip6_input.c:438 ip6_input_finish net/ipv6/ip6_input.c:483 [inline] NF_HOOK include/linux/netfilter.h:314 [inline] ip6_input+0x15d/0x430 net/ipv6/ip6_input.c:492 ip6_mc_input+0xa7e/0xc80 net/ipv6/ip6_input.c:586 dst_input include/net/dst.h:460 [inline] ip6_rcv_finish+0x955/0x970 net/ipv6/ip6_input.c:79 NF_HOOK include/linux/netfilter.h:314 [inline] ipv6_rcv+0xde/0x390 net/ipv6/ip6_input.c:310 __netif_receive_skb_one_core net/core/dev.c:5538 [inline] __netif_receive_skb+0x1da/0xa00 net/core/dev.c:5652 netif_receive_skb_internal net/core/dev.c:5738 [inline] netif_receive_skb+0x58/0x660 net/core/dev.c:5798 tun_rx_batched+0x3ee/0x980 drivers/net/tun.c:1549 tun_get_user+0x5566/0x69e0 drivers/net/tun.c:2002 tun_chr_write_iter+0x3af/0x5d0 drivers/net/tun.c:2048 call_write_iter include/linux/fs.h:2108 [inline] new_sync_write fs/read_write.c:497 [inline] vfs_write+0xb63/0x1520 fs/read_write.c:590 ksys_write+0x20f/0x4c0 fs/read_write.c:643 __do_sys_write fs/read_write.c:655 [inline] __se_sys_write fs/read_write.c:652 [inline] __x64_sys_write+0x93/0xe0 fs/read_write.c:652 do_syscall_64+0xd5/0x1f0 entry_SYSCALL_64_after_hwframe+0x6d/0x75 Uninit was created at: slab_post_alloc_hook mm/slub.c:3804 [inline] slab_alloc_node mm/slub.c:3845 [inline] kmem_cache_alloc_node+0x613/0xc50 mm/slub.c:3888 kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:577 __alloc_skb+0x35b/0x7a0 net/core/skbuff.c:668 alloc_skb include/linux/skbuff.h:1318 [inline] alloc_skb_with_frags+0xc8/0xbf0 net/core/skbuff.c:6504 sock_alloc_send_pskb+0xa81/0xbf0 net/core/sock.c:2795 tun_alloc_skb drivers/net/tun.c:1525 [inline] tun_get_user+0x209a/0x69e0 drivers/net/tun.c:1846 tun_chr_write_iter+0x3af/0x5d0 drivers/net/tun.c:2048 call_write_iter include/linux/fs.h:2108 [inline] new_sync_write fs/read_write.c:497 [inline] vfs_write+0xb63/0x1520 fs/read_write.c:590 ksys_write+0x20f/0x4c0 fs/read_write.c:643 __do_sys_write fs/read_write.c:655 [inline] __se_sys_write fs/read_write.c:652 [inline] __x64_sys_write+0x93/0xe0 fs/read_write.c:652 do_syscall_64+0xd5/0x1f0 entry_SYSCALL_64_after_hwframe+0x6d/0x75 CPU: 1 PID: 5045 Comm: syz-executor114 Not tainted 6.9.0-rc1-syzkaller-00021-g962490525cff #0

Timeline

1. May 19, 2024, 8:34 AM UTCCVE published
2. May 7, 2025, 7:58 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: partial

3. Oct 15, 2026, 12:41 AM UTCRecord last updated

Affected versions

• Linux Linux

  From 0a198e0bb8bef51ced179702ad1af6f9e3715b64 · fixed in 06a939f72a24a7d8251f84cf4c042df86c6666ac; From cb73ee40b1b381eaf3749e6dbeed567bb38e5258 · fixed in e54a0c79cdc2548729dd7e2e468b08c5af4d0df5; From cb73ee40b1b381eaf3749e6dbeed567bb38e5258 · fixed in b14b9f9503ec823ca75be766dcaeff4f0bfeca85; From cb73ee40b1b381eaf3749e6dbeed567bb38e5258 · fixed in ee0088101beee10fa809716d6245d915b09c37c7; From cb73ee40b1b381eaf3749e6dbeed567bb38e5258 · fixed in 1db7fcb2b290c47c202b79528824f119fa28937d; From cb73ee40b1b381eaf3749e6dbeed567bb38e5258 · fixed in 4e3fdeecec5707678b0d1f18c259dadb97262e9d; From cb73ee40b1b381eaf3749e6dbeed567bb38e5258 · fixed in 0ac328a5a4138a6c03dfc3f46017bd5c19167446; From cb73ee40b1b381eaf3749e6dbeed567bb38e5258 · fixed in 17af420545a750f763025149fa7b833a4fc8b8f0; From 4.19.20 · fixed in 4.19.312; From 4.20.7 · fixed in 4.21

• Linux Linux

  5.0

• KernelLinux

  fixed in 4.19.312; From 4.20.0 · fixed in 5.4.274; From 5.0.0 · fixed in 5.10.215; From 5.5.0 · fixed in 5.15.154; From 5.11.0 · fixed in 6.1.85; From 5.16.0 · fixed in 6.6.26; From 6.2.0 · fixed in 6.8.5

References 8