GHSA-86FR-X2QV-CXP5

Vulnerability from github – Published: 2024-03-25 12:30 – Updated: 2025-03-13 21:31
VLAI?
Details

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

tipc: skb_linearize the head skb when reassembling msgs

It's not a good idea to append the frag skb to a skb's frag_list if the frag_list already has skbs from elsewhere, such as this skb was created by pskb_copy() where the frag_list was cloned (all the skbs in it were skb_get'ed) and shared by multiple skbs.

However, the new appended frag skb should have been only seen by the current skb. Otherwise, it will cause use after free crashes as this appended frag skb are seen by multiple skbs but it only got skb_get called once.

The same thing happens with a skb updated by pskb_may_pull() with a skb_cloned skb. Li Shuang has reported quite a few crashes caused by this when doing testing over macvlan devices:

[] kernel BUG at net/core/skbuff.c:1970! [] Call Trace: [] skb_clone+0x4d/0xb0 [] macvlan_broadcast+0xd8/0x160 [macvlan] [] macvlan_process_broadcast+0x148/0x150 [macvlan] [] process_one_work+0x1a7/0x360 [] worker_thread+0x30/0x390

[] kernel BUG at mm/usercopy.c:102! [] Call Trace: [] __check_heap_object+0xd3/0x100 [] __check_object_size+0xff/0x16b [] simple_copy_to_iter+0x1c/0x30 [] __skb_datagram_iter+0x7d/0x310 [] __skb_datagram_iter+0x2a5/0x310 [] skb_copy_datagram_iter+0x3b/0x90 [] tipc_recvmsg+0x14a/0x3a0 [tipc] [] _sysrecvmsg+0x91/0x150 [] _sys_recvmsg+0x7b/0xc0

[] kernel BUG at mm/slub.c:305! [] Call Trace: [] [] kmem_cache_free+0x3ff/0x400 [] __netif_receive_skb_core+0x12c/0xc40 [] ? kmem_cache_alloc+0x12e/0x270 [] netif_receive_skb_internal+0x3d/0xb0 [] ? get_rx_page_info+0x8e/0xa0 [be2net] [] be_poll+0x6ef/0xd00 [be2net] [] ? irq_exit+0x4f/0x100 [] net_rx_action+0x149/0x3b0

...

This patch is to fix it by linearizing the head skb if it has frag_list set in tipc_buf_append(). Note that we choose to do this before calling skb_unshare(), as __skb_linearize() will avoid skb_copy(). Also, we can not just drop the frag_list either as the early time.

Severity ?
5.5 (Medium)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
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{
  "affected": [],
  "aliases": [
    "CVE-2021-47162"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-416"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2024-03-25T10:15:08Z",
    "severity": "MODERATE"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ntipc: skb_linearize the head skb when reassembling msgs\n\nIt\u0027s not a good idea to append the frag skb to a skb\u0027s frag_list if\nthe frag_list already has skbs from elsewhere, such as this skb was\ncreated by pskb_copy() where the frag_list was cloned (all the skbs\nin it were skb_get\u0027ed) and shared by multiple skbs.\n\nHowever, the new appended frag skb should have been only seen by the\ncurrent skb. Otherwise, it will cause use after free crashes as this\nappended frag skb are seen by multiple skbs but it only got skb_get\ncalled once.\n\nThe same thing happens with a skb updated by pskb_may_pull() with a\nskb_cloned skb. Li Shuang has reported quite a few crashes caused\nby this when doing testing over macvlan devices:\n\n  [] kernel BUG at net/core/skbuff.c:1970!\n  [] Call Trace:\n  []  skb_clone+0x4d/0xb0\n  []  macvlan_broadcast+0xd8/0x160 [macvlan]\n  []  macvlan_process_broadcast+0x148/0x150 [macvlan]\n  []  process_one_work+0x1a7/0x360\n  []  worker_thread+0x30/0x390\n\n  [] kernel BUG at mm/usercopy.c:102!\n  [] Call Trace:\n  []  __check_heap_object+0xd3/0x100\n  []  __check_object_size+0xff/0x16b\n  []  simple_copy_to_iter+0x1c/0x30\n  []  __skb_datagram_iter+0x7d/0x310\n  []  __skb_datagram_iter+0x2a5/0x310\n  []  skb_copy_datagram_iter+0x3b/0x90\n  []  tipc_recvmsg+0x14a/0x3a0 [tipc]\n  []  ____sys_recvmsg+0x91/0x150\n  []  ___sys_recvmsg+0x7b/0xc0\n\n  [] kernel BUG at mm/slub.c:305!\n  [] Call Trace:\n  []  \u003cIRQ\u003e\n  []  kmem_cache_free+0x3ff/0x400\n  []  __netif_receive_skb_core+0x12c/0xc40\n  []  ? kmem_cache_alloc+0x12e/0x270\n  []  netif_receive_skb_internal+0x3d/0xb0\n  []  ? get_rx_page_info+0x8e/0xa0 [be2net]\n  []  be_poll+0x6ef/0xd00 [be2net]\n  []  ? irq_exit+0x4f/0x100\n  []  net_rx_action+0x149/0x3b0\n\n  ...\n\nThis patch is to fix it by linearizing the head skb if it has frag_list\nset in tipc_buf_append(). Note that we choose to do this before calling\nskb_unshare(), as __skb_linearize() will avoid skb_copy(). Also, we can\nnot just drop the frag_list either as the early time.",
  "id": "GHSA-86fr-x2qv-cxp5",
  "modified": "2025-03-13T21:31:02Z",
  "published": "2024-03-25T12:30:51Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-47162"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/436d650d374329a591c30339a91fa5078052ed1e"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4b1761898861117c97066aea6c58f68a7787f0bf"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5489f30bb78ff0dafb4229a69632afc2ba20765c"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/64d17ec9f1ded042c4b188d15734f33486ed9966"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6da24cfc83ba4f97ea44fc7ae9999a006101755c"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ace300eecbccaa698e2b472843c74a5f33f7dce8"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b2c8d28c34b3070407cb1741f9ba3f15d0284b8b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b7df21cf1b79ab7026f545e7bf837bd5750ac026"
    }
  ],
  "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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