In 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:
<TASK>
__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.
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:
<TASK>
__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.
Metrics
Affected Vendors & Products
Advisories
| Source | ID | Title |
|---|---|---|
EUVD |
EUVD-2025-27882 | In 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: <TASK> __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. |
Ubuntu USN |
USN-7833-1 | Linux kernel vulnerabilities |
Ubuntu USN |
USN-7834-1 | Linux kernel (Azure) vulnerabilities |
Ubuntu USN |
USN-7833-2 | Linux kernel (Real-time) vulnerabilities |
Ubuntu USN |
USN-7833-3 | Linux kernel (AWS) vulnerabilities |
Ubuntu USN |
USN-7833-4 | Linux kernel (GCP) vulnerabilities |
Ubuntu USN |
USN-7856-1 | Linux kernel (HWE) vulnerabilities |
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Tue, 18 Nov 2025 22:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-1188 | |
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.16:rc1:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.16:rc2:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.16:rc3:*:*:*:*:*:* |
Mon, 18 Aug 2025 21:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| First Time appeared |
Linux
Linux linux Kernel |
|
| Vendors & Products |
Linux
Linux linux Kernel |
Mon, 18 Aug 2025 12:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| References |
| |
| Metrics |
threat_severity
|
cvssV3_1
|
Sat, 16 Aug 2025 11:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In 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: <TASK> __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. | |
| Title | cifs: Fix the smbd_response slab to allow usercopy | |
| References |
|
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2025-08-16T11:12:17.254Z
Reserved: 2025-04-16T04:51:24.023Z
Link: CVE-2025-38523
No data.
Status : Analyzed
Published: 2025-08-16T12:15:27.667
Modified: 2025-11-18T21:53:29.273
Link: CVE-2025-38523
OpenCVE Enrichment
Updated: 2025-08-18T20:50:01Z
EUVD
Ubuntu USN