afs: Protect call->state changes against signals

Protect call->state changes against the call being prematurely terminated
due to a signal.

What can happen is that a signal causes afs_wait_for_call_to_complete() to
abort an afs_call because it's not yet complete whilst afs_deliver_to_call()
is delivering data to that call.

If the data delivery causes the state to change, this may overwrite the state
of the afs_call, making it not-yet-complete again - but no further
notifications will be forthcoming from AF_RXRPC as the rxrpc call has been
aborted and completed, so kAFS will just hang in various places waiting for
that call or on page bits that need clearing by that call.

A tracepoint to monitor call state changes is also provided.

Signed-off-by: David Howells <dhowells@redhat.com>

1 files changed, 12 insertions, 14 deletions

diff --git a/fs/afs/cmservice.c b/fs/afs/cmservice.c
index 5767f540e0e1..41e277f57b20 100644
--- a/fs/afs/cmservice.c
+++ b/fs/afs/cmservice.c
@@ -188,7 +188,6 @@ static int afs_deliver_cb_callback(struct afs_call *call)
 
         switch (call->unmarshall) {
         case 0:
-                rxrpc_kernel_get_peer(call->net->socket, call->rxcall, &srx);
                 call->offset = 0;
                 call->unmarshall++;
 
@@ -281,10 +280,12 @@ static int afs_deliver_cb_callback(struct afs_call *call)
                 break;
         }
 
-        call->state = AFS_CALL_REPLYING;
+        if (!afs_check_call_state(call, AFS_CALL_SV_REPLYING))
+                return -EIO;
 
         /* we'll need the file server record as that tells us which set of
          * vnodes to operate upon */
+        rxrpc_kernel_get_peer(call->net->socket, call->rxcall, &srx);
         server = afs_find_server(call->net, &srx);
         if (!server)
                 return -ENOTCONN;
@@ -325,9 +326,6 @@ static int afs_deliver_cb_init_call_back_state(struct afs_call *call)
         if (ret < 0)
                 return ret;
 
-        /* no unmarshalling required */
-        call->state = AFS_CALL_REPLYING;
-
         /* we'll need the file server record as that tells us which set of
          * vnodes to operate upon */
         server = afs_find_server(call->net, &srx);
@@ -352,8 +350,6 @@ static int afs_deliver_cb_init_call_back_state3(struct afs_call *call)
 
         _enter("");
 
-        rxrpc_kernel_get_peer(call->net->socket, call->rxcall, &srx);
-
         _enter("{%u}", call->unmarshall);
 
         switch (call->unmarshall) {
@@ -397,11 +393,12 @@ static int afs_deliver_cb_init_call_back_state3(struct afs_call *call)
                 break;
         }
 
-        /* no unmarshalling required */
-        call->state = AFS_CALL_REPLYING;
+        if (!afs_check_call_state(call, AFS_CALL_SV_REPLYING))
+                return -EIO;
 
         /* we'll need the file server record as that tells us which set of
          * vnodes to operate upon */
+        rxrpc_kernel_get_peer(call->net->socket, call->rxcall, &srx);
         server = afs_find_server(call->net, &srx);
         if (!server)
                 return -ENOTCONN;
@@ -436,8 +433,8 @@ static int afs_deliver_cb_probe(struct afs_call *call)
         if (ret < 0)
                 return ret;
 
-        /* no unmarshalling required */
-        call->state = AFS_CALL_REPLYING;
+        if (!afs_check_call_state(call, AFS_CALL_SV_REPLYING))
+                return -EIO;
 
         return afs_queue_call_work(call);
 }
@@ -519,7 +516,8 @@ static int afs_deliver_cb_probe_uuid(struct afs_call *call)
                 break;
         }
 
-        call->state = AFS_CALL_REPLYING;
+        if (!afs_check_call_state(call, AFS_CALL_SV_REPLYING))
+                return -EIO;
 
         return afs_queue_call_work(call);
 }
@@ -600,8 +598,8 @@ static int afs_deliver_cb_tell_me_about_yourself(struct afs_call *call)
         if (ret < 0)
                 return ret;
 
-        /* no unmarshalling required */
-        call->state = AFS_CALL_REPLYING;
+        if (!afs_check_call_state(call, AFS_CALL_SV_REPLYING))
+                return -EIO;
 
         return afs_queue_call_work(call);
 }