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author | David Howells <dhowells@redhat.com> | 2017-11-02 15:06:08 +0000 |
---|---|---|
committer | David Howells <dhowells@redhat.com> | 2017-11-02 15:07:18 +0000 |
commit | 20acbd9a7aeee0b0af7107f3de791a52c949f3ac (patch) | |
tree | 654bcbd298a68ae8f44d161536cc16f66692e7fd | |
parent | 2d2faaf0568b4946d9abeb4e541227b4ca259840 (diff) | |
download | op-kernel-dev-20acbd9a7aeee0b0af7107f3de791a52c949f3ac.zip op-kernel-dev-20acbd9a7aeee0b0af7107f3de791a52c949f3ac.tar.gz |
rxrpc: Lock around calling a kernel service Rx notification
Place a spinlock around the invocation of call->notify_rx() for a kernel
service call and lock again when ending the call and replace the
notification pointer with a pointer to a dummy function.
This is required because it's possible for rxrpc_notify_socket() to be
called after the call has been ended by the kernel service if called from
the asynchronous work function rxrpc_process_call().
However, rxrpc_notify_socket() currently only holds the RCU read lock when
invoking ->notify_rx(), which means that the afs_call struct would need to
be disposed of by call_rcu() rather than by kfree().
But we shouldn't see any notifications from a call after calling
rxrpc_kernel_end_call(), so a lock is required in rxrpc code.
Without this, we may see the call wait queue as having a corrupt spinlock:
BUG: spinlock bad magic on CPU#0, kworker/0:2/1612
general protection fault: 0000 [#1] SMP
...
Workqueue: krxrpcd rxrpc_process_call
task: ffff88040b83c400 task.stack: ffff88040adfc000
RIP: 0010:spin_bug+0x161/0x18f
RSP: 0018:ffff88040adffcc0 EFLAGS: 00010002
RAX: 0000000000000032 RBX: 6b6b6b6b6b6b6b6b RCX: ffffffff81ab16cf
RDX: ffff88041fa14c01 RSI: ffff88041fa0ccb8 RDI: ffff88041fa0ccb8
RBP: ffff88040adffcd8 R08: 00000000ffffffff R09: 00000000ffffffff
R10: ffff88040adffc60 R11: 000000000000022c R12: ffff88040aca2208
R13: ffffffff81a58114 R14: 0000000000000000 R15: 0000000000000000
....
Call Trace:
do_raw_spin_lock+0x1d/0x89
_raw_spin_lock_irqsave+0x3d/0x49
? __wake_up_common_lock+0x4c/0xa7
__wake_up_common_lock+0x4c/0xa7
? __lock_is_held+0x47/0x7a
__wake_up+0xe/0x10
afs_wake_up_call_waiter+0x11b/0x122 [kafs]
rxrpc_notify_socket+0x12b/0x258
rxrpc_process_call+0x18e/0x7d0
process_one_work+0x298/0x4de
? rescuer_thread+0x280/0x280
worker_thread+0x1d1/0x2ae
? rescuer_thread+0x280/0x280
kthread+0x12c/0x134
? kthread_create_on_node+0x3a/0x3a
ret_from_fork+0x27/0x40
In this case, note the corrupt data in EBX. The address of the offending
afs_call is in R12, plus the offset to the spinlock.
Signed-off-by: David Howells <dhowells@redhat.com>
-rw-r--r-- | net/rxrpc/af_rxrpc.c | 16 | ||||
-rw-r--r-- | net/rxrpc/ar-internal.h | 1 | ||||
-rw-r--r-- | net/rxrpc/call_object.c | 1 | ||||
-rw-r--r-- | net/rxrpc/recvmsg.c | 2 |
4 files changed, 20 insertions, 0 deletions
diff --git a/net/rxrpc/af_rxrpc.c b/net/rxrpc/af_rxrpc.c index 344b2dc..9b5c46b 100644 --- a/net/rxrpc/af_rxrpc.c +++ b/net/rxrpc/af_rxrpc.c @@ -322,6 +322,14 @@ struct rxrpc_call *rxrpc_kernel_begin_call(struct socket *sock, } EXPORT_SYMBOL(rxrpc_kernel_begin_call); +/* + * Dummy function used to stop the notifier talking to recvmsg(). + */ +static void rxrpc_dummy_notify_rx(struct sock *sk, struct rxrpc_call *rxcall, + unsigned long call_user_ID) +{ +} + /** * rxrpc_kernel_end_call - Allow a kernel service to end a call it was using * @sock: The socket the call is on @@ -336,6 +344,14 @@ void rxrpc_kernel_end_call(struct socket *sock, struct rxrpc_call *call) mutex_lock(&call->user_mutex); rxrpc_release_call(rxrpc_sk(sock->sk), call); + + /* Make sure we're not going to call back into a kernel service */ + if (call->notify_rx) { + spin_lock_bh(&call->notify_lock); + call->notify_rx = rxrpc_dummy_notify_rx; + spin_unlock_bh(&call->notify_lock); + } + mutex_unlock(&call->user_mutex); rxrpc_put_call(call, rxrpc_call_put_kernel); } diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h index ea5600b..b215199 100644 --- a/net/rxrpc/ar-internal.h +++ b/net/rxrpc/ar-internal.h @@ -525,6 +525,7 @@ struct rxrpc_call { unsigned long flags; unsigned long events; spinlock_t lock; + spinlock_t notify_lock; /* Kernel notification lock */ rwlock_t state_lock; /* lock for state transition */ u32 abort_code; /* Local/remote abort code */ int error; /* Local error incurred */ diff --git a/net/rxrpc/call_object.c b/net/rxrpc/call_object.c index fcdd655..4c7fbc6 100644 --- a/net/rxrpc/call_object.c +++ b/net/rxrpc/call_object.c @@ -124,6 +124,7 @@ struct rxrpc_call *rxrpc_alloc_call(gfp_t gfp) INIT_LIST_HEAD(&call->sock_link); init_waitqueue_head(&call->waitq); spin_lock_init(&call->lock); + spin_lock_init(&call->notify_lock); rwlock_init(&call->state_lock); atomic_set(&call->usage, 1); call->debug_id = atomic_inc_return(&rxrpc_debug_id); diff --git a/net/rxrpc/recvmsg.c b/net/rxrpc/recvmsg.c index e4937b3..8510a98 100644 --- a/net/rxrpc/recvmsg.c +++ b/net/rxrpc/recvmsg.c @@ -40,7 +40,9 @@ void rxrpc_notify_socket(struct rxrpc_call *call) sk = &rx->sk; if (rx && sk->sk_state < RXRPC_CLOSE) { if (call->notify_rx) { + spin_lock_bh(&call->notify_lock); call->notify_rx(sk, call, call->user_call_ID); + spin_unlock_bh(&call->notify_lock); } else { write_lock_bh(&rx->recvmsg_lock); if (list_empty(&call->recvmsg_link)) { |