Commit 88f17081 authored by Marios Makassikis's avatar Marios Makassikis Committed by Steve French
Browse files

ksmbd: fix recursive locking in RPC handle list access 



Since commit 305853cc ("ksmbd: Fix race condition in RPC handle list
access"), ksmbd_session_rpc_method() attempts to lock sess->rpc_lock.

This causes hung connections / tasks when a client attempts to open
a named pipe. Using Samba's rpcclient tool:

 $ rpcclient //192.168.1.254 -U user%password
 $ rpcclient $> srvinfo
 <connection hung here>

Kernel side:
  "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
  task:kworker/0:0 state:D stack:0 pid:5021 tgid:5021 ppid:2 flags:0x00200000
  Workqueue: ksmbd-io handle_ksmbd_work
  Call trace:
  __schedule from schedule+0x3c/0x58
  schedule from schedule_preempt_disabled+0xc/0x10
  schedule_preempt_disabled from rwsem_down_read_slowpath+0x1b0/0x1d8
  rwsem_down_read_slowpath from down_read+0x28/0x30
  down_read from ksmbd_session_rpc_method+0x18/0x3c
  ksmbd_session_rpc_method from ksmbd_rpc_open+0x34/0x68
  ksmbd_rpc_open from ksmbd_session_rpc_open+0x194/0x228
  ksmbd_session_rpc_open from create_smb2_pipe+0x8c/0x2c8
  create_smb2_pipe from smb2_open+0x10c/0x27ac
  smb2_open from handle_ksmbd_work+0x238/0x3dc
  handle_ksmbd_work from process_scheduled_works+0x160/0x25c
  process_scheduled_works from worker_thread+0x16c/0x1e8
  worker_thread from kthread+0xa8/0xb8
  kthread from ret_from_fork+0x14/0x38
  Exception stack(0x8529ffb0 to 0x8529fff8)

The task deadlocks because the lock is already held:
  ksmbd_session_rpc_open
    down_write(&sess->rpc_lock)
    ksmbd_rpc_open
      ksmbd_session_rpc_method
        down_read(&sess->rpc_lock)   <-- deadlock

Adjust ksmbd_session_rpc_method() callers to take the lock when necessary.

Fixes: 305853cc ("ksmbd: Fix race condition in RPC handle list access")
Signed-off-by: default avatarMarios Makassikis <mmakassikis@freebox.fr>
Acked-by: default avatarNamjae Jeon <linkinjeon@kernel.org>
Signed-off-by: default avatarSteve French <stfrench@microsoft.com>
parent 379510a8

fs/smb/server/mgmt/user_session.c

+2 −5
Original line number Diff line number Diff line
@@ -147,14 +147,11 @@ void ksmbd_session_rpc_close(struct ksmbd_session *sess, int id) 
int ksmbd_session_rpc_method(struct ksmbd_session *sess, int id)

{

	struct ksmbd_session_rpc *entry;

	int method;



	down_read(&sess->rpc_lock);

	lockdep_assert_held(&sess->rpc_lock);

	entry = xa_load(&sess->rpc_handle_list, id);

	method = entry ? entry->method : 0;

	up_read(&sess->rpc_lock);



	return method;

	return entry ? entry->method : 0;

}



void ksmbd_session_destroy(struct ksmbd_session *sess)

fs/smb/server/smb2pdu.c

+8 −1
Original line number Diff line number Diff line
@@ -4626,8 +4626,15 @@ static int smb2_get_info_file_pipe(struct ksmbd_session *sess, 
	 * pipe without opening it, checking error condition here

	 */

	id = req->VolatileFileId;

	if (!ksmbd_session_rpc_method(sess, id))



	lockdep_assert_not_held(&sess->rpc_lock);



	down_read(&sess->rpc_lock);

	if (!ksmbd_session_rpc_method(sess, id)) {

		up_read(&sess->rpc_lock);

		return -ENOENT;

	}

	up_read(&sess->rpc_lock);



	ksmbd_debug(SMB, "FileInfoClass %u, FileId 0x%llx\n",

		    req->FileInfoClass, req->VolatileFileId);

fs/smb/server/transport_ipc.c

+12 −0
Original line number Diff line number Diff line
@@ -825,6 +825,9 @@ struct ksmbd_rpc_command *ksmbd_rpc_write(struct ksmbd_session *sess, int handle 
	if (!msg)

		return NULL;



	lockdep_assert_not_held(&sess->rpc_lock);



	down_read(&sess->rpc_lock);

	msg->type = KSMBD_EVENT_RPC_REQUEST;

	req = (struct ksmbd_rpc_command *)msg->payload;

	req->handle = handle;
@@ -833,6 +836,7 @@ struct ksmbd_rpc_command *ksmbd_rpc_write(struct ksmbd_session *sess, int handle 
	req->flags |= KSMBD_RPC_WRITE_METHOD;

	req->payload_sz = payload_sz;

	memcpy(req->payload, payload, payload_sz);

	up_read(&sess->rpc_lock);



	resp = ipc_msg_send_request(msg, req->handle);

	ipc_msg_free(msg);
@@ -849,6 +853,9 @@ struct ksmbd_rpc_command *ksmbd_rpc_read(struct ksmbd_session *sess, int handle) 
	if (!msg)

		return NULL;



	lockdep_assert_not_held(&sess->rpc_lock);



	down_read(&sess->rpc_lock);

	msg->type = KSMBD_EVENT_RPC_REQUEST;

	req = (struct ksmbd_rpc_command *)msg->payload;

	req->handle = handle;
@@ -856,6 +863,7 @@ struct ksmbd_rpc_command *ksmbd_rpc_read(struct ksmbd_session *sess, int handle) 
	req->flags |= rpc_context_flags(sess);

	req->flags |= KSMBD_RPC_READ_METHOD;

	req->payload_sz = 0;

	up_read(&sess->rpc_lock);



	resp = ipc_msg_send_request(msg, req->handle);

	ipc_msg_free(msg);
@@ -876,6 +884,9 @@ struct ksmbd_rpc_command *ksmbd_rpc_ioctl(struct ksmbd_session *sess, int handle 
	if (!msg)

		return NULL;



	lockdep_assert_not_held(&sess->rpc_lock);



	down_read(&sess->rpc_lock);

	msg->type = KSMBD_EVENT_RPC_REQUEST;

	req = (struct ksmbd_rpc_command *)msg->payload;

	req->handle = handle;
@@ -884,6 +895,7 @@ struct ksmbd_rpc_command *ksmbd_rpc_ioctl(struct ksmbd_session *sess, int handle 
	req->flags |= KSMBD_RPC_IOCTL_METHOD;

	req->payload_sz = payload_sz;

	memcpy(req->payload, payload, payload_sz);

	up_read(&sess->rpc_lock);



	resp = ipc_msg_send_request(msg, req->handle);

	ipc_msg_free(msg);