CVE-2025-21961

In the Linux kernel, the following vulnerability has been resolved:

eth: bnxt: fix truesize for mb-xdp-pass case

When mb-xdp is set and return is XDP_PASS, packet is converted from xdp_buff to sk_buff with xdp_update_skb_shared_info() in bnxt_xdp_build_skb(). bnxt_xdp_build_skb() passes incorrect truesize argument to xdp_update_skb_shared_info(). The truesize is calculated as BNXT_RX_PAGE_SIZE * sinfo->nr_frags but the skb_shared_info was wiped by napi_build_skb() before. So it stores sinfo->nr_frags before bnxt_xdp_build_skb() and use it instead of getting skb_shared_info from xdp_get_shared_info_from_buff().

Splat looks like: ------------[ cut here ]------------ WARNING: CPU: 2 PID: 0 at net/core/skbuff.c:6072 skb_try_coalesce+0x504/0x590 Modules linked in: xt_nat xt_tcpudp veth af_packet xt_conntrack nft_chain_nat xt_MASQUERADE nf_conntrack_netlink xfrm_user xt_addrtype nft_coms CPU: 2 UID: 0 PID: 0 Comm: swapper/2 Not tainted 6.14.0-rc2+ #3 RIP: 0010:skb_try_coalesce+0x504/0x590 Code: 4b fd ff ff 49 8b 34 24 40 80 e6 40 0f 84 3d fd ff ff 49 8b 74 24 48 40 f6 c6 01 0f 84 2e fd ff ff 48 8d 4e ff e9 25 fd ff ff <0f> 0b e99 RSP: 0018:ffffb62c4120caa8 EFLAGS: 00010287 RAX: 0000000000000003 RBX: ffffb62c4120cb14 RCX: 0000000000000ec0 RDX: 0000000000001000 RSI: ffffa06e5d7dc000 RDI: 0000000000000003 RBP: ffffa06e5d7ddec0 R08: ffffa06e6120a800 R09: ffffa06e7a119900 R10: 0000000000002310 R11: ffffa06e5d7dcec0 R12: ffffe4360575f740 R13: ffffe43600000000 R14: 0000000000000002 R15: 0000000000000002 FS: 0000000000000000(0000) GS:ffffa0755f700000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f147b76b0f8 CR3: 00000001615d4000 CR4: 00000000007506f0 PKRU: 55555554 Call Trace: <IRQ> ? __warn+0x84/0x130 ? skb_try_coalesce+0x504/0x590 ? report_bug+0x18a/0x1a0 ? handle_bug+0x53/0x90 ? exc_invalid_op+0x14/0x70 ? asm_exc_invalid_op+0x16/0x20 ? skb_try_coalesce+0x504/0x590 inet_frag_reasm_finish+0x11f/0x2e0 ip_defrag+0x37a/0x900 ip_local_deliver+0x51/0x120 ip_sublist_rcv_finish+0x64/0x70 ip_sublist_rcv+0x179/0x210 ip_list_rcv+0xf9/0x130

How to reproduce: <Node A> ip link set $interface1 xdp obj xdp_pass.o ip link set $interface1 mtu 9000 up ip a a 10.0.0.1/24 dev $interface1 <Node B> ip link set $interfac2 mtu 9000 up ip a a 10.0.0.2/24 dev $interface2 ping 10.0.0.1 -s 65000

Following ping.py patch adds xdp-mb-pass case. so ping.py is going to be able to reproduce this issue.

This vulnerability is rated as Moderate impact for Red Hat Enterprise Linux because triggering the flaw requires specific physical network hardware and an administrative, non-default eBPF configuration. The flaw resides in the Broadcom NetXtreme (bnxt_en) driver when processing jumbo frames through a multi-buffer eXpress Data Path program that passes packets to the kernel network stack. Because XDP programs are not configured by default and require privileged access to attach, typical deployments and systems using alternative network hardware are not exposed.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this issue, prevent module bnxt_en from being loaded. Please see https://access.redhat.com/solutions/41278 for how to blacklist a kernel module to prevent it from loading automatically.