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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 /net/rxrpc/recvmsg.c | |
| parent | 2d2faaf0568b4946d9abeb4e541227b4ca259840 (diff) | |
| download | linux-rt-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>
Diffstat (limited to 'net/rxrpc/recvmsg.c')
| -rw-r--r-- | net/rxrpc/recvmsg.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/net/rxrpc/recvmsg.c b/net/rxrpc/recvmsg.c index e4937b3f3685..8510a98b87e1 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)) { |