fkie_cve-2025-40271
Vulnerability from fkie_nvd
Published
2025-12-06 22:15
Modified
2025-12-08 18:26
Severity ?
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 |
|---|
{
"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)"
}
],
"id": "CVE-2025-40271",
"lastModified": "2025-12-08T18:26:49.133",
"metrics": {},
"published": "2025-12-06T22:15:54.737",
"references": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"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"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Awaiting Analysis"
}
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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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