Linux Kernel CVE-2025-68263

In the Linux kernel, the following vulnerability has been resolved:

ksmbd: ipc: fix use-after-free in ipc_msg_send_request

ipc_msg_send_request() waits for a generic netlink reply using an ipc_msg_table_entry on the stack. The generic netlink handler (handle_generic_event()/handle_response()) fills entry->response under ipc_msg_table_lock, but ipc_msg_send_request() used to validate and free entry->response without holding the same lock.

Under high concurrency this allows a race where handle_response() is copying data into entry->response while ipc_msg_send_request() has just freed it, leading to a slab-use-after-free reported by KASAN in handle_generic_event():

BUG: KASAN: slab-use-after-free in handle_generic_event+0x3c4/0x5f0 [ksmbd] Write of size 12 at addr ffff888198ee6e20 by task pool/109349 ... Freed by task: kvfree ipc_msg_send_request [ksmbd] ksmbd_rpc_open -> ksmbd_session_rpc_open [ksmbd]

Fix by:

• Taking ipc_msg_table_lock in ipc_msg_send_request() while validating

entry->response, freeing it when invalid, and removing the entry from ipc_msg_table.

• Returning the final entry->response pointer to the caller only after

the hash entry is removed under the lock.

• Returning NULL in the error path, preserving the original API

semantics.

This makes all accesses to entry->response consistent with handle_response(), which already updates and fills the response buffer under ipc_msg_table_lock, and closes the race that allowed the UAF.

Linux kernel versions running the ksmbd module are affected, specifically stable kernel branches as evidenced by commits to multiple stable trees (commit hashes 1fab1fa091f5, 5ac763713a1e, 708a620b471a, 759c8c30cfa8, 8229c6ca50ce, de85fb58f996 across different branches). The ksmbd feature was introduced in Linux 5.15 and is present in subsequent mainline and long-term support kernels. Exact vulnerable version ranges are not explicitly provided in available data, but the presence of patches across multiple stable branches suggests the vulnerability existed in ksmbd since its introduction and affects 5.15+ kernels prior to patched versions. Only systems with ksmbd enabled and actively serving SMB traffic are exploitable. Vendor advisories available at the provided kernel.org git stable references.