ghsa-8gwc-c833-gwmc
Vulnerability from github
Published
2025-09-18 15:30
Modified
2025-09-29 12:30
Details

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

net: sched: fix memory leak in tcindex_set_parms

Syzkaller reports a memory leak as follows:

BUG: memory leak unreferenced object 0xffff88810c287f00 (size 256): comm "syz-executor105", pid 3600, jiffies 4294943292 (age 12.990s) hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace: [] kmalloc_trace+0x20/0x90 mm/slab_common.c:1046 [] kmalloc include/linux/slab.h:576 [inline] [] kmalloc_array include/linux/slab.h:627 [inline] [] kcalloc include/linux/slab.h:659 [inline] [] tcf_exts_init include/net/pkt_cls.h:250 [inline] [] tcindex_set_parms+0xa7/0xbe0 net/sched/cls_tcindex.c:342 [] tcindex_change+0xdf/0x120 net/sched/cls_tcindex.c:553 [] tc_new_tfilter+0x4f2/0x1100 net/sched/cls_api.c:2147 [] rtnetlink_rcv_msg+0x4dc/0x5d0 net/core/rtnetlink.c:6082 [] netlink_rcv_skb+0x87/0x1d0 net/netlink/af_netlink.c:2540 [] netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] [] netlink_unicast+0x397/0x4c0 net/netlink/af_netlink.c:1345 [] netlink_sendmsg+0x396/0x710 net/netlink/af_netlink.c:1921 [] sock_sendmsg_nosec net/socket.c:714 [inline] [] sock_sendmsg+0x56/0x80 net/socket.c:734 [] _syssendmsg+0x178/0x410 net/socket.c:2482 [] _sys_sendmsg+0xa8/0x110 net/socket.c:2536 [] __sys_sendmmsg+0x105/0x330 net/socket.c:2622 [] __do_sys_sendmmsg net/socket.c:2651 [inline] [] __se_sys_sendmmsg net/socket.c:2648 [inline] [] __x64_sys_sendmmsg+0x24/0x30 net/socket.c:2648 [] do_syscall_x64 arch/x86/entry/common.c:50 [inline] [] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 [] entry_SYSCALL_64_after_hwframe+0x63/0xcd ====================================

Kernel uses tcindex_change() to change an existing filter properties.

Yet the problem is that, during the process of changing, if old_r is retrieved from p->perfect, then kernel uses tcindex_alloc_perfect_hash() to newly allocate filter results, uses tcindex_filter_result_init() to clear the old filter result, without destroying its tcf_exts structure, which triggers the above memory leak.

To be more specific, there are only two source for the old_r, according to the tcindex_lookup(). old_r is retrieved from p->perfect, or old_r is retrieved from p->h.

  • If old_r is retrieved from p->perfect, kernel uses tcindex_alloc_perfect_hash() to newly allocate the filter results. Then r is assigned with cp->perfect + handle, which is newly allocated. So condition old_r && old_r != r is true in this situation, and kernel uses tcindex_filter_result_init() to clear the old filter result, without destroying its tcf_exts structure

  • If old_r is retrieved from p->h, then p->perfect is NULL according to the tcindex_lookup(). Considering that cp->h is directly copied from p->h and p->perfect is NULL, r is assigned with tcindex_lookup(cp, handle), whose value should be the same as old_r, so condition old_r && old_r != r is false in this situation, kernel ignores using tcindex_filter_result_init() to clear the old filter result.

So only when old_r is retrieved from p->perfect does kernel use tcindex_filter_result_init() to clear the old filter result, which triggers the above memory leak.

Considering that there already exists a tc_filter_wq workqueue to destroy the old tcindex_d ---truncated---

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{
  "affected": [],
  "aliases": [
    "CVE-2022-50396"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-09-18T14:15:38Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: sched: fix memory leak in tcindex_set_parms\n\nSyzkaller reports a memory leak as follows:\n====================================\nBUG: memory leak\nunreferenced object 0xffff88810c287f00 (size 256):\n  comm \"syz-executor105\", pid 3600, jiffies 4294943292 (age 12.990s)\n  hex dump (first 32 bytes):\n    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................\n    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................\n  backtrace:\n    [\u003cffffffff814cf9f0\u003e] kmalloc_trace+0x20/0x90 mm/slab_common.c:1046\n    [\u003cffffffff839c9e07\u003e] kmalloc include/linux/slab.h:576 [inline]\n    [\u003cffffffff839c9e07\u003e] kmalloc_array include/linux/slab.h:627 [inline]\n    [\u003cffffffff839c9e07\u003e] kcalloc include/linux/slab.h:659 [inline]\n    [\u003cffffffff839c9e07\u003e] tcf_exts_init include/net/pkt_cls.h:250 [inline]\n    [\u003cffffffff839c9e07\u003e] tcindex_set_parms+0xa7/0xbe0 net/sched/cls_tcindex.c:342\n    [\u003cffffffff839caa1f\u003e] tcindex_change+0xdf/0x120 net/sched/cls_tcindex.c:553\n    [\u003cffffffff8394db62\u003e] tc_new_tfilter+0x4f2/0x1100 net/sched/cls_api.c:2147\n    [\u003cffffffff8389e91c\u003e] rtnetlink_rcv_msg+0x4dc/0x5d0 net/core/rtnetlink.c:6082\n    [\u003cffffffff839eba67\u003e] netlink_rcv_skb+0x87/0x1d0 net/netlink/af_netlink.c:2540\n    [\u003cffffffff839eab87\u003e] netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]\n    [\u003cffffffff839eab87\u003e] netlink_unicast+0x397/0x4c0 net/netlink/af_netlink.c:1345\n    [\u003cffffffff839eb046\u003e] netlink_sendmsg+0x396/0x710 net/netlink/af_netlink.c:1921\n    [\u003cffffffff8383e796\u003e] sock_sendmsg_nosec net/socket.c:714 [inline]\n    [\u003cffffffff8383e796\u003e] sock_sendmsg+0x56/0x80 net/socket.c:734\n    [\u003cffffffff8383eb08\u003e] ____sys_sendmsg+0x178/0x410 net/socket.c:2482\n    [\u003cffffffff83843678\u003e] ___sys_sendmsg+0xa8/0x110 net/socket.c:2536\n    [\u003cffffffff838439c5\u003e] __sys_sendmmsg+0x105/0x330 net/socket.c:2622\n    [\u003cffffffff83843c14\u003e] __do_sys_sendmmsg net/socket.c:2651 [inline]\n    [\u003cffffffff83843c14\u003e] __se_sys_sendmmsg net/socket.c:2648 [inline]\n    [\u003cffffffff83843c14\u003e] __x64_sys_sendmmsg+0x24/0x30 net/socket.c:2648\n    [\u003cffffffff84605fd5\u003e] do_syscall_x64 arch/x86/entry/common.c:50 [inline]\n    [\u003cffffffff84605fd5\u003e] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80\n    [\u003cffffffff84800087\u003e] entry_SYSCALL_64_after_hwframe+0x63/0xcd\n====================================\n\nKernel uses tcindex_change() to change an existing\nfilter properties.\n\nYet the problem is that, during the process of changing,\nif `old_r` is retrieved from `p-\u003eperfect`, then\nkernel uses tcindex_alloc_perfect_hash() to newly\nallocate filter results, uses tcindex_filter_result_init()\nto clear the old filter result, without destroying\nits tcf_exts structure, which triggers the above memory leak.\n\nTo be more specific, there are only two source for the `old_r`,\naccording to the tcindex_lookup(). `old_r` is retrieved from\n`p-\u003eperfect`, or `old_r` is retrieved from `p-\u003eh`.\n\n  * If `old_r` is retrieved from `p-\u003eperfect`, kernel uses\ntcindex_alloc_perfect_hash() to newly allocate the\nfilter results. Then `r` is assigned with `cp-\u003eperfect + handle`,\nwhich is newly allocated. So condition `old_r \u0026\u0026 old_r != r` is\ntrue in this situation, and kernel uses tcindex_filter_result_init()\nto clear the old filter result, without destroying\nits tcf_exts structure\n\n  * If `old_r` is retrieved from `p-\u003eh`, then `p-\u003eperfect` is NULL\naccording to the tcindex_lookup(). Considering that `cp-\u003eh`\nis directly copied from `p-\u003eh` and `p-\u003eperfect` is NULL,\n`r` is assigned with `tcindex_lookup(cp, handle)`, whose value\nshould be the same as `old_r`, so condition `old_r \u0026\u0026 old_r != r`\nis false in this situation, kernel ignores using\ntcindex_filter_result_init() to clear the old filter result.\n\nSo only when `old_r` is retrieved from `p-\u003eperfect` does kernel use\ntcindex_filter_result_init() to clear the old filter result, which\ntriggers the above memory leak.\n\nConsidering that there already exists a tc_filter_wq workqueue\nto destroy the old tcindex_d\n---truncated---",
  "id": "GHSA-8gwc-c833-gwmc",
  "modified": "2025-09-29T12:30:26Z",
  "published": "2025-09-18T15:30:33Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2022-50396"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/01d0d2b8b4e3cf2110baba9371c0c3d04ad5c77b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/18c3fa7a7fdbb4d21dafc8a7710ae2c1680930f6"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/372ae77cf11d11fb118cbe2d37def9dd5f826abd"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/399ab7fe0fa0d846881685fd4e57e9a8ef7559f7"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3abebc503a5148072052c229c6b04b329a420ecd"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/53af9c793f644d5841d84d8e0ad83bd7ab47f3e0"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/55ac68b53f1cea1926ee2313afc5d66b91daad71"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6c55953e232ea668731091d111066521f3b7719b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/7a6fb69bbcb21e9ce13bdf18c008c268874f0480"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/7c183dc0af472dec33d2c0786a5e356baa8cad19"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b314f6c3512108d7a656c5caf07c82d1bbbdc0f1"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c4de6057e7c6654983acb63d939d26ac0d7bbf39"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/facc4405e8b7407e03216207b1d1d640127de0c8"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}


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