GHSA-CHR3-3876-PRR8
Vulnerability from github – Published: 2025-04-01 18:30 – Updated: 2026-07-14 15:31In the Linux kernel, the following vulnerability has been resolved:
llc: do not use skb_get() before dev_queue_xmit()
syzbot is able to crash hosts [1], using llc and devices not supporting IFF_TX_SKB_SHARING.
In this case, e1000 driver calls eth_skb_pad(), while the skb is shared.
Simply replace skb_get() by skb_clone() in net/llc/llc_s_ac.c
Note that e1000 driver might have an issue with pktgen, because it does not clear IFF_TX_SKB_SHARING, this is an orthogonal change.
We need to audit other skb_get() uses in net/llc.
[1]
kernel BUG at net/core/skbuff.c:2178 ! Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN NOPTI CPU: 0 UID: 0 PID: 16371 Comm: syz.2.2764 Not tainted 6.14.0-rc4-syzkaller-00052-gac9c34d1e45a #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 RIP: 0010:pskb_expand_head+0x6ce/0x1240 net/core/skbuff.c:2178 Call Trace: __skb_pad+0x18a/0x610 net/core/skbuff.c:2466 __skb_put_padto include/linux/skbuff.h:3843 [inline] skb_put_padto include/linux/skbuff.h:3862 [inline] eth_skb_pad include/linux/etherdevice.h:656 [inline] e1000_xmit_frame+0x2d99/0x5800 drivers/net/ethernet/intel/e1000/e1000_main.c:3128 __netdev_start_xmit include/linux/netdevice.h:5151 [inline] netdev_start_xmit include/linux/netdevice.h:5160 [inline] xmit_one net/core/dev.c:3806 [inline] dev_hard_start_xmit+0x9a/0x7b0 net/core/dev.c:3822 sch_direct_xmit+0x1ae/0xc30 net/sched/sch_generic.c:343 __dev_xmit_skb net/core/dev.c:4045 [inline] __dev_queue_xmit+0x13d4/0x43e0 net/core/dev.c:4621 dev_queue_xmit include/linux/netdevice.h:3313 [inline] llc_sap_action_send_test_c+0x268/0x320 net/llc/llc_s_ac.c:144 llc_exec_sap_trans_actions net/llc/llc_sap.c:153 [inline] llc_sap_next_state net/llc/llc_sap.c:182 [inline] llc_sap_state_process+0x239/0x510 net/llc/llc_sap.c:209 llc_ui_sendmsg+0xd0d/0x14e0 net/llc/af_llc.c:993 sock_sendmsg_nosec net/socket.c:718 [inline]
{
"affected": [],
"aliases": [
"CVE-2025-21925"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-04-01T16:15:23Z",
"severity": "MODERATE"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nllc: do not use skb_get() before dev_queue_xmit()\n\nsyzbot is able to crash hosts [1], using llc and devices\nnot supporting IFF_TX_SKB_SHARING.\n\nIn this case, e1000 driver calls eth_skb_pad(), while\nthe skb is shared.\n\nSimply replace skb_get() by skb_clone() in net/llc/llc_s_ac.c\n\nNote that e1000 driver might have an issue with pktgen,\nbecause it does not clear IFF_TX_SKB_SHARING, this is an\northogonal change.\n\nWe need to audit other skb_get() uses in net/llc.\n\n[1]\n\nkernel BUG at net/core/skbuff.c:2178 !\nOops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN NOPTI\nCPU: 0 UID: 0 PID: 16371 Comm: syz.2.2764 Not tainted 6.14.0-rc4-syzkaller-00052-gac9c34d1e45a #0\nHardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014\n RIP: 0010:pskb_expand_head+0x6ce/0x1240 net/core/skbuff.c:2178\nCall Trace:\n \u003cTASK\u003e\n __skb_pad+0x18a/0x610 net/core/skbuff.c:2466\n __skb_put_padto include/linux/skbuff.h:3843 [inline]\n skb_put_padto include/linux/skbuff.h:3862 [inline]\n eth_skb_pad include/linux/etherdevice.h:656 [inline]\n e1000_xmit_frame+0x2d99/0x5800 drivers/net/ethernet/intel/e1000/e1000_main.c:3128\n __netdev_start_xmit include/linux/netdevice.h:5151 [inline]\n netdev_start_xmit include/linux/netdevice.h:5160 [inline]\n xmit_one net/core/dev.c:3806 [inline]\n dev_hard_start_xmit+0x9a/0x7b0 net/core/dev.c:3822\n sch_direct_xmit+0x1ae/0xc30 net/sched/sch_generic.c:343\n __dev_xmit_skb net/core/dev.c:4045 [inline]\n __dev_queue_xmit+0x13d4/0x43e0 net/core/dev.c:4621\n dev_queue_xmit include/linux/netdevice.h:3313 [inline]\n llc_sap_action_send_test_c+0x268/0x320 net/llc/llc_s_ac.c:144\n llc_exec_sap_trans_actions net/llc/llc_sap.c:153 [inline]\n llc_sap_next_state net/llc/llc_sap.c:182 [inline]\n llc_sap_state_process+0x239/0x510 net/llc/llc_sap.c:209\n llc_ui_sendmsg+0xd0d/0x14e0 net/llc/af_llc.c:993\n sock_sendmsg_nosec net/socket.c:718 [inline]",
"id": "GHSA-chr3-3876-prr8",
"modified": "2026-07-14T15:31:20Z",
"published": "2025-04-01T18:30:51Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-21925"
},
{
"type": "WEB",
"url": "https://cert-portal.siemens.com/productcert/html/ssa-019113.html"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/056e8a46d79e22983bae4267e0d9c52927076f46"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/0f764208dc24ea043c3e20194d32aebf94f8459c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/13f3f872627f0f27c31245524fc11367756240ad"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/17f86e25431ebc15aa9245ff156414fdad47822d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/416e8b4c20c6398044e93008deefd563289f477d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/64e6a754d33d31aa844b3ee66fb93ac84ca1565e"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9b6f083db141ece0024be01526aa05aa978811cb"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/cd1c44327bbbd50fc24f2b38892f5f328b784d0f"
},
{
"type": "WEB",
"url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html"
},
{
"type": "WEB",
"url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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