Описание
In the Linux kernel, the following vulnerability has been resolved: smb/client: fix memory leak in smb2_open_file() Reproducer:
- server: directories are exported read-only
- client: mount -t cifs //${server_ip}/export /mnt
- client: dd if=/dev/zero of=/mnt/file bs=512 count=1000 oflag=direct
- client: umount /mnt
- client: sleep 1
- client: modprobe -r cifs The error message is as follows: ============================================================================= BUG cifs_small_rq (Not tainted): Objects remaining on __kmem_cache_shutdown()
Object 0x00000000d47521be @offset=14336
...
WARNING: mm/slub.c:1251 at __kmem_cache_shutdown+0x34e/0x440, CPU#0: modprobe/1577
...
Call Trace:
kmem_cache_destroy+0x94/0x190
cifs_destroy_request_bufs+0x3e/0x50 [cifs]
cleanup_module+0x4e/0x540 [cifs]
__se_sys_delete_module+0x278/0x400
__x64_sys_delete_module+0x5f/0x70
x64_sys_call+0x2299/0x2ff0
do_syscall_64+0x89/0x350
entry_SYSCALL_64_after_hwframe+0x76/0x7e
...
kmem_cache_destroy cifs_small_rq: Slab cache still has objects when called from cifs_destroy_request_bufs+0x3e/0x50 [cifs]
WARNING: mm/slab_common.c:532 at kmem_cache_destroy+0x16b/0x190, CPU#0: modprobe/1577
A memory leak flaw was found in the Linux kernel's CIFS/SMB client. In the smb2_open_file() function, request buffers are not properly freed when performing direct I/O writes to a read-only SMB share. This causes slab cache objects to remain allocated, which can prevent the cifs module from unloading cleanly and lead to gradual memory exhaustion with repeated operations.
Отчет
Exploitation requires mounting an SMB share and performing specific I/O patterns (direct writes to read-only exports). The memory leak manifests primarily when unloading the cifs module, making it a reliability issue rather than a readily exploitable denial of service condition.
Меры по смягчению последствий
To mitigate this issue, prevent the cifs module from being loaded. See https://access.redhat.com/solutions/41278 for instructions on how to blacklist kernel modules.
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| Red Hat Enterprise Linux 6 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 8 | kernel | Not affected | ||
| Red Hat Enterprise Linux 8 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 9 | kernel-rt | Fix deferred | ||
| Red Hat Enterprise Linux 10 | kernel | Fixed | RHSA-2025:20095 | 11.11.2025 |
| Red Hat Enterprise Linux 9 | kernel | Fixed | RHSA-2025:20518 | 11.11.2025 |
| Red Hat Enterprise Linux 9 | kernel | Fixed | RHSA-2025:20518 | 11.11.2025 |
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Дополнительная информация
Статус:
EPSS
5.5 Medium
CVSS3
Связанные уязвимости
In the Linux kernel, the following vulnerability has been resolved: smb/client: fix memory leak in smb2_open_file() Reproducer: 1. server: directories are exported read-only 2. client: mount -t cifs //${server_ip}/export /mnt 3. client: dd if=/dev/zero of=/mnt/file bs=512 count=1000 oflag=direct 4. client: umount /mnt 5. client: sleep 1 6. client: modprobe -r cifs The error message is as follows: ============================================================================= BUG cifs_small_rq (Not tainted): Objects remaining on __kmem_cache_shutdown() ----------------------------------------------------------------------------- Object 0x00000000d47521be @offset=14336 ... WARNING: mm/slub.c:1251 at __kmem_cache_shutdown+0x34e/0x440, CPU#0: modprobe/1577 ... Call Trace: <TASK> kmem_cache_destroy+0x94/0x190 cifs_destroy_request_bufs+0x3e/0x50 [cifs] cleanup_module+0x4e/0x540 [cifs] __se_sys_delete_module+0x278/0x400 __x64_sys_delete_module+0x5f/0x70 x64_sys_call+0x2299/0x2ff0 do_syscall_...
In the Linux kernel, the following vulnerability has been resolved: smb/client: fix memory leak in smb2_open_file() Reproducer: 1. server: directories are exported read-only 2. client: mount -t cifs //${server_ip}/export /mnt 3. client: dd if=/dev/zero of=/mnt/file bs=512 count=1000 oflag=direct 4. client: umount /mnt 5. client: sleep 1 6. client: modprobe -r cifs The error message is as follows: ============================================================================= BUG cifs_small_rq (Not tainted): Objects remaining on __kmem_cache_shutdown() ----------------------------------------------------------------------------- Object 0x00000000d47521be @offset=14336 ... WARNING: mm/slub.c:1251 at __kmem_cache_shutdown+0x34e/0x440, CPU#0: modprobe/1577 ... Call Trace: <TASK> kmem_cache_destroy+0x94/0x190 cifs_destroy_request_bufs+0x3e/0x50 [cifs] cleanup_module+0x4e/0x540 [cifs] __se_sys_delete_module+0x278/0x400 __x64_sys_delete_module
In the Linux kernel, the following vulnerability has been resolved: s ...
In the Linux kernel, the following vulnerability has been resolved: smb/client: fix memory leak in smb2_open_file() Reproducer: 1. server: directories are exported read-only 2. client: mount -t cifs //${server_ip}/export /mnt 3. client: dd if=/dev/zero of=/mnt/file bs=512 count=1000 oflag=direct 4. client: umount /mnt 5. client: sleep 1 6. client: modprobe -r cifs The error message is as follows: ============================================================================= BUG cifs_small_rq (Not tainted): Objects remaining on __kmem_cache_shutdown() ----------------------------------------------------------------------------- Object 0x00000000d47521be @offset=14336 ... WARNING: mm/slub.c:1251 at __kmem_cache_shutdown+0x34e/0x440, CPU#0: modprobe/1577 ... Call Trace: <TASK> kmem_cache_destroy+0x94/0x190 cifs_destroy_request_bufs+0x3e/0x50 [cifs] cleanup_module+0x4e/0x540 [cifs] __se_sys_delete_module+0x278/0x400 __x64_sys_delete_mod...
EPSS
5.5 Medium
CVSS3