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.