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authorDavid Howells <dhowells@redhat.com>2017-11-02 15:06:08 +0000
committerDavid Howells <dhowells@redhat.com>2017-11-02 15:07:18 +0000
commit20acbd9a7aeee0b0af7107f3de791a52c949f3ac (patch)
tree654bcbd298a68ae8f44d161536cc16f66692e7fd /net/rxrpc/call_object.c
parent2d2faaf0568b4946d9abeb4e541227b4ca259840 (diff)
downloadlinux-stericsson-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/call_object.c')
-rw-r--r--net/rxrpc/call_object.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/net/rxrpc/call_object.c b/net/rxrpc/call_object.c
index fcdd6555a820..4c7fbc6dcce7 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);