From: David Howells <dhowells@xxxxxxxxxx> [ Upstream commit 610a79ffea02102899a1373fe226d949944a7ed6 ] afs_wake_up_async_call() can incur lock recursion. The problem is that it is called from AF_RXRPC whilst holding the ->notify_lock, but it tries to take a ref on the afs_call struct in order to pass it to a work queue - but if the afs_call is already queued, we then have an extraneous ref that must be put... calling afs_put_call() may call back down into AF_RXRPC through rxrpc_kernel_shutdown_call(), however, which might try taking the ->notify_lock again. This case isn't very common, however, so defer it to a workqueue. The oops looks something like: BUG: spinlock recursion on CPU#0, krxrpcio/7001/1646 lock: 0xffff888141399b30, .magic: dead4ead, .owner: krxrpcio/7001/1646, .owner_cpu: 0 CPU: 0 UID: 0 PID: 1646 Comm: krxrpcio/7001 Not tainted 6.12.0-rc2-build3+ #4351 Hardware name: ASUS All Series/H97-PLUS, BIOS 2306 10/09/2014 Call Trace: <TASK> dump_stack_lvl+0x47/0x70 do_raw_spin_lock+0x3c/0x90 rxrpc_kernel_shutdown_call+0x83/0xb0 afs_put_call+0xd7/0x180 rxrpc_notify_socket+0xa0/0x190 rxrpc_input_split_jumbo+0x198/0x1d0 rxrpc_input_data+0x14b/0x1e0 ? rxrpc_input_call_packet+0xc2/0x1f0 rxrpc_input_call_event+0xad/0x6b0 rxrpc_input_packet_on_conn+0x1e1/0x210 rxrpc_input_packet+0x3f2/0x4d0 rxrpc_io_thread+0x243/0x410 ? __pfx_rxrpc_io_thread+0x10/0x10 kthread+0xcf/0xe0 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x24/0x40 ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1a/0x30 </TASK> Signed-off-by: David Howells <dhowells@xxxxxxxxxx> Link: https://lore.kernel.org/r/1394602.1729162732@xxxxxxxxxxxxxxxxxxxxxx cc: Marc Dionne <marc.dionne@xxxxxxxxxxxx> cc: linux-afs@xxxxxxxxxxxxxxxxxxx cc: linux-fsdevel@xxxxxxxxxxxxxxx Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- fs/afs/internal.h | 2 ++ fs/afs/rxrpc.c | 83 +++++++++++++++++++++++++++++++++-------------- 2 files changed, 61 insertions(+), 24 deletions(-) diff --git a/fs/afs/internal.h b/fs/afs/internal.h index 6e1d3c4daf72c..52aab09a32a92 100644 --- a/fs/afs/internal.h +++ b/fs/afs/internal.h @@ -130,6 +130,7 @@ struct afs_call { wait_queue_head_t waitq; /* processes awaiting completion */ struct work_struct async_work; /* async I/O processor */ struct work_struct work; /* actual work processor */ + struct work_struct free_work; /* Deferred free processor */ struct rxrpc_call *rxcall; /* RxRPC call handle */ struct rxrpc_peer *peer; /* Remote endpoint */ struct key *key; /* security for this call */ @@ -1331,6 +1332,7 @@ extern int __net_init afs_open_socket(struct afs_net *); extern void __net_exit afs_close_socket(struct afs_net *); extern void afs_charge_preallocation(struct work_struct *); extern void afs_put_call(struct afs_call *); +void afs_deferred_put_call(struct afs_call *call); void afs_make_call(struct afs_call *call, gfp_t gfp); void afs_wait_for_call_to_complete(struct afs_call *call); extern struct afs_call *afs_alloc_flat_call(struct afs_net *, diff --git a/fs/afs/rxrpc.c b/fs/afs/rxrpc.c index c453428f3c8ba..9f2a3bb56ec69 100644 --- a/fs/afs/rxrpc.c +++ b/fs/afs/rxrpc.c @@ -18,6 +18,7 @@ struct workqueue_struct *afs_async_calls; +static void afs_deferred_free_worker(struct work_struct *work); static void afs_wake_up_call_waiter(struct sock *, struct rxrpc_call *, unsigned long); static void afs_wake_up_async_call(struct sock *, struct rxrpc_call *, unsigned long); static void afs_process_async_call(struct work_struct *); @@ -149,6 +150,7 @@ static struct afs_call *afs_alloc_call(struct afs_net *net, call->debug_id = atomic_inc_return(&rxrpc_debug_id); refcount_set(&call->ref, 1); INIT_WORK(&call->async_work, afs_process_async_call); + INIT_WORK(&call->free_work, afs_deferred_free_worker); init_waitqueue_head(&call->waitq); spin_lock_init(&call->state_lock); call->iter = &call->def_iter; @@ -159,6 +161,36 @@ static struct afs_call *afs_alloc_call(struct afs_net *net, return call; } +static void afs_free_call(struct afs_call *call) +{ + struct afs_net *net = call->net; + int o; + + ASSERT(!work_pending(&call->async_work)); + + rxrpc_kernel_put_peer(call->peer); + + if (call->rxcall) { + rxrpc_kernel_shutdown_call(net->socket, call->rxcall); + rxrpc_kernel_put_call(net->socket, call->rxcall); + call->rxcall = NULL; + } + if (call->type->destructor) + call->type->destructor(call); + + afs_unuse_server_notime(call->net, call->server, afs_server_trace_put_call); + kfree(call->request); + + o = atomic_read(&net->nr_outstanding_calls); + trace_afs_call(call->debug_id, afs_call_trace_free, 0, o, + __builtin_return_address(0)); + kfree(call); + + o = atomic_dec_return(&net->nr_outstanding_calls); + if (o == 0) + wake_up_var(&net->nr_outstanding_calls); +} + /* * Dispose of a reference on a call. */ @@ -173,32 +205,34 @@ void afs_put_call(struct afs_call *call) o = atomic_read(&net->nr_outstanding_calls); trace_afs_call(debug_id, afs_call_trace_put, r - 1, o, __builtin_return_address(0)); + if (zero) + afs_free_call(call); +} - if (zero) { - ASSERT(!work_pending(&call->async_work)); - ASSERT(call->type->name != NULL); - - rxrpc_kernel_put_peer(call->peer); - - if (call->rxcall) { - rxrpc_kernel_shutdown_call(net->socket, call->rxcall); - rxrpc_kernel_put_call(net->socket, call->rxcall); - call->rxcall = NULL; - } - if (call->type->destructor) - call->type->destructor(call); +static void afs_deferred_free_worker(struct work_struct *work) +{ + struct afs_call *call = container_of(work, struct afs_call, free_work); - afs_unuse_server_notime(call->net, call->server, afs_server_trace_put_call); - kfree(call->request); + afs_free_call(call); +} - trace_afs_call(call->debug_id, afs_call_trace_free, 0, o, - __builtin_return_address(0)); - kfree(call); +/* + * Dispose of a reference on a call, deferring the cleanup to a workqueue + * to avoid lock recursion. + */ +void afs_deferred_put_call(struct afs_call *call) +{ + struct afs_net *net = call->net; + unsigned int debug_id = call->debug_id; + bool zero; + int r, o; - o = atomic_dec_return(&net->nr_outstanding_calls); - if (o == 0) - wake_up_var(&net->nr_outstanding_calls); - } + zero = __refcount_dec_and_test(&call->ref, &r); + o = atomic_read(&net->nr_outstanding_calls); + trace_afs_call(debug_id, afs_call_trace_put, r - 1, o, + __builtin_return_address(0)); + if (zero) + schedule_work(&call->free_work); } static struct afs_call *afs_get_call(struct afs_call *call, @@ -640,7 +674,8 @@ static void afs_wake_up_call_waiter(struct sock *sk, struct rxrpc_call *rxcall, } /* - * wake up an asynchronous call + * Wake up an asynchronous call. The caller is holding the call notify + * spinlock around this, so we can't call afs_put_call(). */ static void afs_wake_up_async_call(struct sock *sk, struct rxrpc_call *rxcall, unsigned long call_user_ID) @@ -657,7 +692,7 @@ static void afs_wake_up_async_call(struct sock *sk, struct rxrpc_call *rxcall, __builtin_return_address(0)); if (!queue_work(afs_async_calls, &call->async_work)) - afs_put_call(call); + afs_deferred_put_call(call); } } -- 2.43.0
