CVE-2025-68263: 
Linux Debian vulnerability analysis and mitigation

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.