CVE-2025-40271 (GCVE-0-2025-40271)
Vulnerability from cvelistv5
Published
2025-12-06 21:50
Modified
2025-12-06 21:50
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
fs/proc: fix uaf in proc_readdir_de()
Pde is erased from subdir rbtree through rb_erase(), but not set the node
to EMPTY, which may result in uaf access. We should use RB_CLEAR_NODE()
set the erased node to EMPTY, then pde_subdir_next() will return NULL to
avoid uaf access.
We found an uaf issue while using stress-ng testing, need to run testcase
getdent and tun in the same time. The steps of the issue is as follows:
1) use getdent to traverse dir /proc/pid/net/dev_snmp6/, and current
pde is tun3;
2) in the [time windows] unregister netdevice tun3 and tun2, and erase
them from rbtree. erase tun3 first, and then erase tun2. the
pde(tun2) will be released to slab;
3) continue to getdent process, then pde_subdir_next() will return
pde(tun2) which is released, it will case uaf access.
CPU 0 | CPU 1
-------------------------------------------------------------------------
traverse dir /proc/pid/net/dev_snmp6/ | unregister_netdevice(tun->dev) //tun3 tun2
sys_getdents64() |
iterate_dir() |
proc_readdir() |
proc_readdir_de() | snmp6_unregister_dev()
pde_get(de); | proc_remove()
read_unlock(&proc_subdir_lock); | remove_proc_subtree()
| write_lock(&proc_subdir_lock);
[time window] | rb_erase(&root->subdir_node, &parent->subdir);
| write_unlock(&proc_subdir_lock);
read_lock(&proc_subdir_lock); |
next = pde_subdir_next(de); |
pde_put(de); |
de = next; //UAF |
rbtree of dev_snmp6
|
pde(tun3)
/ \
NULL pde(tun2)
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 |
||
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"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfs/proc: fix uaf in proc_readdir_de()\n\nPde is erased from subdir rbtree through rb_erase(), but not set the node\nto EMPTY, which may result in uaf access. We should use RB_CLEAR_NODE()\nset the erased node to EMPTY, then pde_subdir_next() will return NULL to\navoid uaf access.\n\nWe found an uaf issue while using stress-ng testing, need to run testcase\ngetdent and tun in the same time. The steps of the issue is as follows:\n\n1) use getdent to traverse dir /proc/pid/net/dev_snmp6/, and current\n pde is tun3;\n\n2) in the [time windows] unregister netdevice tun3 and tun2, and erase\n them from rbtree. erase tun3 first, and then erase tun2. the\n pde(tun2) will be released to slab;\n\n3) continue to getdent process, then pde_subdir_next() will return\n pde(tun2) which is released, it will case uaf access.\n\nCPU 0 | CPU 1\n-------------------------------------------------------------------------\ntraverse dir /proc/pid/net/dev_snmp6/ | unregister_netdevice(tun-\u003edev) //tun3 tun2\nsys_getdents64() |\n iterate_dir() |\n proc_readdir() |\n proc_readdir_de() | snmp6_unregister_dev()\n pde_get(de); | proc_remove()\n read_unlock(\u0026proc_subdir_lock); | remove_proc_subtree()\n | write_lock(\u0026proc_subdir_lock);\n [time window] | rb_erase(\u0026root-\u003esubdir_node, \u0026parent-\u003esubdir);\n | write_unlock(\u0026proc_subdir_lock);\n read_lock(\u0026proc_subdir_lock); |\n next = pde_subdir_next(de); |\n pde_put(de); |\n de = next; //UAF |\n\nrbtree of dev_snmp6\n |\n pde(tun3)\n / \\\n NULL pde(tun2)"
}
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"dateUpdated": "2025-12-06T21:50:53.266Z",
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"url": "https://git.kernel.org/stable/c/1d1596d68a6f11d28f677eedf6cf5b17dbfeb491"
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"url": "https://git.kernel.org/stable/c/c81d0385500446efe48c305bbb83d47f2ae23a50"
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{
"url": "https://git.kernel.org/stable/c/4cba73c4c89219beef7685a47374bf88b1022369"
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{
"url": "https://git.kernel.org/stable/c/6f2482745e510ae1dacc9b090194b9c5f918d774"
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{
"url": "https://git.kernel.org/stable/c/67272c11f379d9aa5e0f6b16286b9d89b3f76046"
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{
"url": "https://git.kernel.org/stable/c/623bb26127fb581a741e880e1e1a47d79aecb6f8"
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{
"url": "https://git.kernel.org/stable/c/03de7ff197a3d0e17d0d5c58fdac99a63cba8110"
},
{
"url": "https://git.kernel.org/stable/c/895b4c0c79b092d732544011c3cecaf7322c36a1"
}
],
"title": "fs/proc: fix uaf in proc_readdir_de()",
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"cveId": "CVE-2025-40271",
"datePublished": "2025-12-06T21:50:53.266Z",
"dateReserved": "2025-04-16T07:20:57.183Z",
"dateUpdated": "2025-12-06T21:50:53.266Z",
"state": "PUBLISHED"
},
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"nvd": "{\"cve\":{\"id\":\"CVE-2025-40271\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-12-06T22:15:54.737\",\"lastModified\":\"2025-12-06T22:15:54.737\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nfs/proc: fix uaf in proc_readdir_de()\\n\\nPde is erased from subdir rbtree through rb_erase(), but not set the node\\nto EMPTY, which may result in uaf access. We should use RB_CLEAR_NODE()\\nset the erased node to EMPTY, then pde_subdir_next() will return NULL to\\navoid uaf access.\\n\\nWe found an uaf issue while using stress-ng testing, need to run testcase\\ngetdent and tun in the same time. The steps of the issue is as follows:\\n\\n1) use getdent to traverse dir /proc/pid/net/dev_snmp6/, and current\\n pde is tun3;\\n\\n2) in the [time windows] unregister netdevice tun3 and tun2, and erase\\n them from rbtree. erase tun3 first, and then erase tun2. the\\n pde(tun2) will be released to slab;\\n\\n3) continue to getdent process, then pde_subdir_next() will return\\n pde(tun2) which is released, it will case uaf access.\\n\\nCPU 0 | CPU 1\\n-------------------------------------------------------------------------\\ntraverse dir /proc/pid/net/dev_snmp6/ | unregister_netdevice(tun-\u003edev) //tun3 tun2\\nsys_getdents64() |\\n iterate_dir() |\\n proc_readdir() |\\n proc_readdir_de() | snmp6_unregister_dev()\\n pde_get(de); | proc_remove()\\n read_unlock(\u0026proc_subdir_lock); | remove_proc_subtree()\\n | write_lock(\u0026proc_subdir_lock);\\n [time window] | rb_erase(\u0026root-\u003esubdir_node, \u0026parent-\u003esubdir);\\n | write_unlock(\u0026proc_subdir_lock);\\n read_lock(\u0026proc_subdir_lock); |\\n next = pde_subdir_next(de); |\\n pde_put(de); |\\n de = next; //UAF |\\n\\nrbtree of dev_snmp6\\n |\\n pde(tun3)\\n / \\\\\\n NULL pde(tun2)\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/03de7ff197a3d0e17d0d5c58fdac99a63cba8110\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/1d1596d68a6f11d28f677eedf6cf5b17dbfeb491\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/4cba73c4c89219beef7685a47374bf88b1022369\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/623bb26127fb581a741e880e1e1a47d79aecb6f8\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/67272c11f379d9aa5e0f6b16286b9d89b3f76046\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/6f2482745e510ae1dacc9b090194b9c5f918d774\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/895b4c0c79b092d732544011c3cecaf7322c36a1\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/c81d0385500446efe48c305bbb83d47f2ae23a50\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
}
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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