Commit 1fab1fa0 authored by Qianchang Zhao's avatar Qianchang Zhao Committed by Steve French
Browse files

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.

Cc: stable@vger.kernel.org
Reported-by: default avatarQianchang Zhao <pioooooooooip@gmail.com>
Reported-by: default avatarZhitong Liu <liuzhitong1993@gmail.com>
Signed-off-by: default avatarQianchang Zhao <pioooooooooip@gmail.com>
Acked-by: default avatarNamjae Jeon <linkinjeon@kernel.org>
Signed-off-by: default avatarSteve French <stfrench@microsoft.com>
parent dc10cf13

fs/smb/server/transport_ipc.c

+5 −2
Original line number Diff line number Diff line
@@ -553,12 +553,16 @@ static void *ipc_msg_send_request(struct ksmbd_ipc_msg *msg, unsigned int handle 
	up_write(&ipc_msg_table_lock);



	ret = ipc_msg_send(msg);

	if (ret)

	if (ret) {

		down_write(&ipc_msg_table_lock);

		goto out;

	}



	ret = wait_event_interruptible_timeout(entry.wait,

					       entry.response != NULL,

					       IPC_WAIT_TIMEOUT);



	down_write(&ipc_msg_table_lock);

	if (entry.response) {

		ret = ipc_validate_msg(&entry);

		if (ret) {
@@ -567,7 +571,6 @@ static void *ipc_msg_send_request(struct ksmbd_ipc_msg *msg, unsigned int handle 
		}

	}

out:

	down_write(&ipc_msg_table_lock);

	hash_del(&entry.ipc_table_hlist);

	up_write(&ipc_msg_table_lock);

	return entry.response;