CVE-2025-21925

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> llc: do not use skb_get() before dev_queue_xmit()<br /> <br /> syzbot is able to crash hosts [1], using llc and devices<br /> not supporting IFF_TX_SKB_SHARING.<br /> <br /> In this case, e1000 driver calls eth_skb_pad(), while<br /> the skb is shared.<br /> <br /> Simply replace skb_get() by skb_clone() in net/llc/llc_s_ac.c<br /> <br /> Note that e1000 driver might have an issue with pktgen,<br /> because it does not clear IFF_TX_SKB_SHARING, this is an<br /> orthogonal change.<br /> <br /> We need to audit other skb_get() uses in net/llc.<br /> <br /> [1]<br /> <br /> kernel BUG at net/core/skbuff.c:2178 !<br /> Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN NOPTI<br /> CPU: 0 UID: 0 PID: 16371 Comm: syz.2.2764 Not tainted 6.14.0-rc4-syzkaller-00052-gac9c34d1e45a #0<br /> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014<br /> RIP: 0010:pskb_expand_head+0x6ce/0x1240 net/core/skbuff.c:2178<br /> Call Trace:<br /> <br /> __skb_pad+0x18a/0x610 net/core/skbuff.c:2466<br /> __skb_put_padto include/linux/skbuff.h:3843 [inline]<br /> skb_put_padto include/linux/skbuff.h:3862 [inline]<br /> eth_skb_pad include/linux/etherdevice.h:656 [inline]<br /> e1000_xmit_frame+0x2d99/0x5800 drivers/net/ethernet/intel/e1000/e1000_main.c:3128<br /> __netdev_start_xmit include/linux/netdevice.h:5151 [inline]<br /> netdev_start_xmit include/linux/netdevice.h:5160 [inline]<br /> xmit_one net/core/dev.c:3806 [inline]<br /> dev_hard_start_xmit+0x9a/0x7b0 net/core/dev.c:3822<br /> sch_direct_xmit+0x1ae/0xc30 net/sched/sch_generic.c:343<br /> __dev_xmit_skb net/core/dev.c:4045 [inline]<br /> __dev_queue_xmit+0x13d4/0x43e0 net/core/dev.c:4621<br /> dev_queue_xmit include/linux/netdevice.h:3313 [inline]<br /> llc_sap_action_send_test_c+0x268/0x320 net/llc/llc_s_ac.c:144<br /> llc_exec_sap_trans_actions net/llc/llc_sap.c:153 [inline]<br /> llc_sap_next_state net/llc/llc_sap.c:182 [inline]<br /> llc_sap_state_process+0x239/0x510 net/llc/llc_sap.c:209<br /> llc_ui_sendmsg+0xd0d/0x14e0 net/llc/af_llc.c:993<br /> sock_sendmsg_nosec net/socket.c:718 [inline]