Description

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.

References 6

• git.kernel.org https://git.kernel.org/stable/c/1fab1fa091f5aa97265648b53ea031deedd26235
• git.kernel.org https://git.kernel.org/stable/c/5ac763713a1ef8f9a8bda1dbd81f0318d67baa4e
• git.kernel.org https://git.kernel.org/stable/c/708a620b471a14466f1f52c90bf3f65ebdb31460
• git.kernel.org https://git.kernel.org/stable/c/759c8c30cfa8706c518e56f67971b1f0932f4b9b
• git.kernel.org https://git.kernel.org/stable/c/8229c6ca50cea701e25a7ee25f48441b582ec5fa
• git.kernel.org https://git.kernel.org/stable/c/de85fb58f9967ba024bb08e0041613d37b57b4d1

Remediation