GHSA-4X9V-H3R3-C3MF
Vulnerability from github – Published: 2025-08-16 12:30 – Updated: 2025-11-19 00:31In the Linux kernel, the following vulnerability has been resolved:
cifs: Fix the smbd_response slab to allow usercopy
The handling of received data in the smbdirect client code involves using copy_to_iter() to copy data from the smbd_reponse struct's packet trailer to a folioq buffer provided by netfslib that encapsulates a chunk of pagecache.
If, however, CONFIG_HARDENED_USERCOPY=y, this will result in the checks then performed in copy_to_iter() oopsing with something like the following:
CIFS: Attempting to mount //172.31.9.1/test CIFS: VFS: RDMA transport established usercopy: Kernel memory exposure attempt detected from SLUB object 'smbd_response_0000000091e24ea1' (offset 81, size 63)! ------------[ cut here ]------------ kernel BUG at mm/usercopy.c:102! ... RIP: 0010:usercopy_abort+0x6c/0x80 ... Call Trace: __check_heap_object+0xe3/0x120 __check_object_size+0x4dc/0x6d0 smbd_recv+0x77f/0xfe0 [cifs] cifs_readv_from_socket+0x276/0x8f0 [cifs] cifs_read_from_socket+0xcd/0x120 [cifs] cifs_demultiplex_thread+0x7e9/0x2d50 [cifs] kthread+0x396/0x830 ret_from_fork+0x2b8/0x3b0 ret_from_fork_asm+0x1a/0x30
The problem is that the smbd_response slab's packet field isn't marked as being permitted for usercopy.
Fix this by passing parameters to kmem_slab_create() to indicate that copy_to_iter() is permitted from the packet region of the smbd_response slab objects, less the header space.
{
"affected": [],
"aliases": [
"CVE-2025-38523"
],
"database_specific": {
"cwe_ids": [
"CWE-1188"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-08-16T12:15:27Z",
"severity": "MODERATE"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\ncifs: Fix the smbd_response slab to allow usercopy\n\nThe handling of received data in the smbdirect client code involves using\ncopy_to_iter() to copy data from the smbd_reponse struct\u0027s packet trailer\nto a folioq buffer provided by netfslib that encapsulates a chunk of\npagecache.\n\nIf, however, CONFIG_HARDENED_USERCOPY=y, this will result in the checks\nthen performed in copy_to_iter() oopsing with something like the following:\n\n CIFS: Attempting to mount //172.31.9.1/test\n CIFS: VFS: RDMA transport established\n usercopy: Kernel memory exposure attempt detected from SLUB object \u0027smbd_response_0000000091e24ea1\u0027 (offset 81, size 63)!\n ------------[ cut here ]------------\n kernel BUG at mm/usercopy.c:102!\n ...\n RIP: 0010:usercopy_abort+0x6c/0x80\n ...\n Call Trace:\n \u003cTASK\u003e\n __check_heap_object+0xe3/0x120\n __check_object_size+0x4dc/0x6d0\n smbd_recv+0x77f/0xfe0 [cifs]\n cifs_readv_from_socket+0x276/0x8f0 [cifs]\n cifs_read_from_socket+0xcd/0x120 [cifs]\n cifs_demultiplex_thread+0x7e9/0x2d50 [cifs]\n kthread+0x396/0x830\n ret_from_fork+0x2b8/0x3b0\n ret_from_fork_asm+0x1a/0x30\n\nThe problem is that the smbd_response slab\u0027s packet field isn\u0027t marked as\nbeing permitted for usercopy.\n\nFix this by passing parameters to kmem_slab_create() to indicate that\ncopy_to_iter() is permitted from the packet region of the smbd_response\nslab objects, less the header space.",
"id": "GHSA-4x9v-h3r3-c3mf",
"modified": "2025-11-19T00:31:23Z",
"published": "2025-08-16T12:30:32Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-38523"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/43e7e284fc77b710d899569360ea46fa3374ae22"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/87dcc7e33fc3dcb8ed32333cec016528b5bb6ce4"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f0dd353d47f7051afa98c6c60c7486831eb1a410"
}
],
"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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