[PATCH 5.0 11/32] rxrpc: Fix net namespace cleanup

Greg Kroah-Hartman
2019-05-04T10:25:44Z

From: David Howells <dhowells@redhat.com>

[ Upstream commit b13023421b5179413421333f602850914f6a7ad8 ]

In rxrpc_destroy_all_calls(), there are two phases: (1) make sure the
->calls list is empty, emitting error messages if not, and (2) wait for the
RCU cleanup to happen on outstanding calls (ie. ->nr_calls becomes 0).

To avoid taking the call_lock, the function prechecks ->calls and if empty,
it returns to avoid taking the lock - this is wrong, however: it still
needs to go and do the second phase and wait for ->nr_calls to become 0.

Without this, the rxrpc_net struct may get deallocated before we get to the
RCU cleanup for the last calls. This can lead to:

Slab corruption (Not tainted): kmalloc-16k start=ffff88802b178000, len=16384
050: 6b 6b 6b 6b 6b 6b 6b 6b 61 6b 6b 6b 6b 6b 6b 6b kkkkkkkkakkkkkkk

Note the "61" at offset 0x58. This corresponds to the ->nr_calls member of
struct rxrpc_net (which is >9k in size, and thus allocated out of the 16k
slab).

Fix this by flipping the condition on the if-statement, putting the locked
section inside the if-body and dropping the return from there. The
function will then always go on to wait for the RCU cleanup on outstanding
calls.

Fixes: 2baec2c3f854 ("rxrpc: Support network namespacing")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/rxrpc/call_object.c | 38 +++++++++++++++++++-------------------
1 file changed, 19 insertions(+), 19 deletions(-)

--- a/net/rxrpc/call_object.c
+++ b/net/rxrpc/call_object.c
@@ -604,30 +604,30 @@ void rxrpc_destroy_all_calls(struct rxrp

_enter("");

- if (list_empty(&rxnet->calls))
- return;
-
- write_lock(&rxnet->call_lock);
+ if (!list_empty(&rxnet->calls)) {
+ write_lock(&rxnet->call_lock);

- while (!list_empty(&rxnet->calls)) {
- call = list_entry(rxnet->calls.next, struct rxrpc_call, link);
- _debug("Zapping call %p", call);
-
- rxrpc_see_call(call);
- list_del_init(&call->link);
-
- pr_err("Call %p still in use (%d,%s,%lx,%lx)!\n",
- call, atomic_read(&call->usage),
- rxrpc_call_states[call->state],
- call->flags, call->events);
+ while (!list_empty(&rxnet->calls)) {
+ call = list_entry(rxnet->calls.next,
+ struct rxrpc_call, link);
+ _debug("Zapping call %p", call);
+
+ rxrpc_see_call(call);
+ list_del_init(&call->link);
+
+ pr_err("Call %p still in use (%d,%s,%lx,%lx)!\n",
+ call, atomic_read(&call->usage),
+ rxrpc_call_states[call->state],
+ call->flags, call->events);
+
+ write_unlock(&rxnet->call_lock);
+ cond_resched();
+ write_lock(&rxnet->call_lock);
+ }

write_unlock(&rxnet->call_lock);
- cond_resched();
- write_lock(&rxnet->call_lock);
}

- write_unlock(&rxnet->call_lock);
-
atomic_dec(&rxnet->nr_calls);
wait_var_event(&rxnet->nr_calls, !atomic_read(&rxnet->nr_calls));
}